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Marsden Fund NewsletterNo 15 March 2001Contents
The fishy art of sniffing out lunch
Marsden researchers at Auckland University are uncovering the cunning techniques fish use to track down prey, where they simply follow their noses and go with the flow. As part of the study into how fish interpret their watery environment, researchers have been concentrating on the lateral line a unique sensory system updating the fish on water currents. "One aspect of fish behaviour where information about the surrounding water currents proved to be important was in odour-search strategies," said research leader Professor John Montgomery. "Fish often track down food on the basis of smell. However, finding the source of an odour underwater is not easy." As part of the project, PhD student Cindy Baker has been investigating how fish follow their noses. She discovered that when fish detect a smell they first determine the direction of current flow and then swim upstream. When they can no longer detect the odour, fish switch to casting across the current. Once they redetect the odour they simply turn back into the current and continue heading upstream. "This strategy allows the fish to track down the odour source very quickly and with a minimum of effort. This search strategy is based on the fish being able to determine its orientation with respect to the direction of water flow," Professor Montgomery said. "We call this kind of search behaviour odour-released rheotaxis. It recognises the relative contributions of the lateral line and the sense of smell to the behaviour. "It can be difficult conceptualising how fish use the lateral line to perceive movements in the waters around them. Humans have no comparable sensory mechanisms, but one way to think of the sense is to imagine it as 'touch at a distance'." The lateral line sense is made up of two receptor types. The first is superficial neuromasts that occur on the surface of the skin; the second, canal neuromasts, located in canals under the skin. "Canal neuromasts allow the fish to pinpoint small-scale water accelerations and mediate behaviours where information about the position and movement of an object relative to that of the fish is required, for example during schooling and capturing prey," he said. "Finding out what superficial neuromasts are used for had proven to be considerably more difficult. Our research work has solved some of these puzzles." Professor Montgomery said his team's work had demonstrated that superficial neuromasts played an important role in rheotaxis, in which fish move towards a current so they can face upstream. "These receptors allow fish to work out their orientation in relation to the direction of water flow. "This discovery overturned the long-held view that the lateral line sense played no role in the detection of large-scale water currents, and was published in the journal Nature in 1997. "This breakthrough opened up a whole new research avenue and led our research team to set out to answer two further crucial questions." The first of these, which Cindy Baker has answered, was whether information on water currents is linked with other sensory inputs, thereby providing the basis for more complex fish behaviours. The second, which postdoctoral fellow Dr Rainer Voigt and PhD student Guy Carton have been working on, is how information about water currents is encoded by superficial neuromasts. "Voigt and Carton found that the frequency of voltage pulses from superficial neuromasts is linked to the speed of the water flow," he said. "The faster the current the more active the receptors become. The fish is able to sense flow direction because superficial neuromasts have directionality sensitive properties. "Some are aligned along the length of the fish while others are aligned across that axis. Although the researchers have yet to identify the exact mechanism, fish probably determine flow direction by bringing together and analysing the signals from many differently orientated neuromasts. "German researchers recently took these findings one step further, showing that sub-surface canal neuromasts can detect a vibrating stimulus in a background of flowing water. This is a task which the superficial neuromasts cannot do. "These findings published in a recent volume of Nature demonstrate the research opportunities within the field of aquatic sensory biology." For further information contact Professor John Montgomery at the School of Biological Sciences, University of Auckland Tel: (09) 373 7599 ext 7208 Fax: (09) 3737417 Email:j.montgomery@auckland.ac.nz Address: Private Bag 92019, Auckland
A workshop with a difference on Mt Doom
A group of 40 scientists recently gathered to discuss, report and collaborate in their research on the mathematical problems of biology, phylogeny and genome analysis. The meeting was held on the volcanic plateau nestled in the shadow of Mt Ngauruhoe (Mt Doom in the film Lord of the Rings). Hosted by the Skotel Resort in Whakapapa Village and financially assisted by the Marsden Fund, the gathering was organised by researchers from Massey University and the University of Canterbury. It was the fifth such annual meeting in New Zealand. The discussions proved just as diverse and interesting as in previous years. Research reports ranged from those on the earliest origins of life to the evolution of New Zealand animal and plant biota. Other subjects included HIV evolution, the complex evolution of mass coral spawnings and zebra fish, bird migrations and glacial refugia, human genome analyses and the maths needed to cope with our increasing understanding of the complexity of life on Earth. Professor David Penny pinpointed areas of research where mathematical models were still underdeveloped, He urged the interdisciplinary audience to work towards improved mathematical descriptions of biology. The message was well taken and understood by those present, many of whom make the annual pilgrimage to New Zealand to participate in the workshop. The appeal is that it is one of the few international meetings where interdisciplinary problem solving comes easily. Controversial issues often receive some of their earliest public airings at workshops of this kind. This year attention was drawn to the controversy surrounding the remains and DNA analyses of the 60,000 year-old Australian aboriginal "Mungo Man". Other hottopics included the observation that global climate change can be accurately predicted without consideration of carbon dioxide levels, the question of whether human activity contributes to global warming, the number of times HIV has jumped the species barrier, and the argument over the relative quality of data generated by the public domain and CELERA human genome projects. Since overseas researchers typically pay their own way to come to these meetings, it means that financial help from Marsden supports the involvement of New Zealand students. This provides them with a great opportunity to actively participate in major scientific discussions of the day and is an important aspect of these workshops. Plans are afoot to continue the tradition next year. The website for the conference, which includes abstracts, is http://imbs.massey.ac.nz/Doom.htm Big results from nanotechnology meetingA major workshop co-organised by the University of Canterbury's Nanostructure Engineering, Science and Technology, (NEST) group will provide major benefits for the local nanotechnology community. The Advanced Research Workshop in Semiconductor Nanostructures was held at the Millennium Hotel, Queenstown, early in February. A group of 120 of the world's leading scientists and engineers in nanotechnology attended the meeting, along with more than 20 local students. Dr Simon Brown, Canterbury University Physics and Astronomy lecturer and principal investigator on a large nanotechnology contract funded by Marsden, hailed the meeting as a great success. "The students who attended the conference had an unparalleled opportunity to meet top people in the field. They saw some spectacular new scientific results being announced," he said. The benefits of the meeting are already becoming clear. Leading edge groups in North America and Europe have now offered samples to the University's NEST group for collaborative research. The Canterbury group has also been asked, along with a top German group, to participate in a Canadian multimillion dollar bid for new equipment. This would give the Canterbury group access to state of the art nanofabrication facilities not yet available in New Zealand. One of the highlights of the meeting came when Klaus von Klitzing, winner of the Nobel Prize for physics in 1985, told of his discovery of a new kind of magnetism that existed only in two-dimensional electron systems. Simon Brown said the conference would have a major impact on the local nanotechnology community. "Around the world nanotechnology is recognized alongside information technology and biotechnology as one of the keys to economic growth over the next 50 years. This conference was another step to developing New Zealand's nanotechnology base." Research by Emma Tankersley News from Marsden Cottageby Dr Valda McCann, Manager, Marsden Fund Marsden CommitteeSeven of the ten Marsden Committee members finished their terms at the end of 2000. The Minister of Research, Science and Technology, Hon. Pete Hodgson, has invited three members to serve on the Committee again. Currently, the Minister is looking at a plan to appoint a further four members as soon as possible, in a way that provides for continuity in the Committee. In the meantime, until all appointments to the Committee have been made, the following panel convenors have been appointed: Dr David Wratt, NIWA (Earth Sciences & Astronomy); Mr Jonathon Mane-Wheoki, University of Canterbury (Humanities); and Professor Anne Smith, University of Otago (Social Sciences). All other panellists and the Committee members are listed on our web-site. Preliminary applicationsThis year we have seen a 17 percent increase in the number of preliminary proposals submitted to Marsden, with an overwhelming response to the new Fast-Start programme for researchers at the beginning of their careers. Invitations to submit full proposals will be sent to applicants after the Marsden Committee meeting in early April. Data on preliminary proposals, by panel, for 2000 and 2001, is listed in the table. The numbers include proposals sent to more than one panel so the total is more than the number of separate proposals which was 756 in 2000 and 885 (708 standard proposals and 177 Fast-start proposals) in 2001.
Editor departsRedmer Yska, who has edited the last ten issues of Marsden Fund Update, is stepping down after this issue. Red was appointed in October 1998 to upgrade the newsletter and to make it more accessible to a wide audience, including the media, schools, libraries and researchers in other disciplines. Many stories published in Update have subsequently been followed up by news media. Thank you, Red for your commitment to Marsden, and your skills and enthusiasm. Good luck with Red Inc and Associates. Kia ora! Marsden up North
Both these people have contributed significant samples of wood to Jonathan, giving him access to the samples vitally needed for his research. Their interest in the progress of his research is a good example of how research can interact with the wider community. How dynamics drive enzyme activityEnzymes are proteins that provide the working machinery of all liv- ing cells. They catalyse the hundreds of reactions by which nutrients are processed, energy is stored and new molecules are made. As part of a Marsden project, an international research group centred at the University of Waikato is determining how the flexibility of enzymes relates to the way they function. At Waikato the work involves Professor Roy Daniel and Drs Warren Tully, Gerrard Selleck, Judy Bragger, and Rachel Dunn, and Colin Monk. Other team members include Professor John Finney at University College London, Professor John Smith and Dr Jennifer Hayward at the University of Heidelberg, and Drs Valérie Réat and Michel Ferrand at the Institut Laue-Langevin in Grenoble. To date the group's main research tool has been the parallel study of enzyme dynamics and enzyme activity, under identical conditions. The dynamics are obtained using neutron scattering, in which atomic movements within the protein cause changes in the direction and speed of a beam of neutrons. "Current thinking relating dynamics to activity tells us that enzymes need to be flexible enough to be catalytically active, but not so flexible that they denature and break down," Professor Daniel said. "This explains why enzymes tend to denature 20°C above their 'design' temperature. Too much stability would mean not enough flexibility for effective catalysis, too little stability means too short a useful lifetime. This nicely explains many observations, including the higher stability but lower activity of heat-tolerant enzymes. "Proteins exhibit a variety of internal atomic vibrations that cover a thousand-fold range of amplitudes (up to 10 nm) and a wide range of frequencies (from 1 to 1015 Hz). We don't know which of these motions are essential for enzymatic activity. Little work has been done relating enzyme catalysis to its flexibility." Professor Daniel said the group used neutron scattering to determine enzyme dynamics over a wide range of temperatures under conditions where activity could also be measured. This work was carried out at the Institut Laue-Langevin, Grenoble, the world's most advanced neutron source. "We have been able to show that the fastest motions that take place within enzymes are not needed for catalysis. "We did this by cooling an enzyme to minus 50°C, where fast motions ceased, and found that the enzyme kept working. In fact, although the activity slows down, it continues to work down to at least minus100°C. "Our lowest temperature achieved, minus 100°C, is the lowest temperature at which enzyme activity has ever been measured. "We have not yet developed techniques to measure enzyme activity below this temperature, which would allow us to 'freeze out' some of the slower motions. "We know that the aqueous environment of enzymes plays an important role in their structure, and therefore their function. To determine enzyme activity at low temperatures we use water/organic solvent mixtures to prevent freezing." Professor Daniel said that an unexpected finding of the work was that variation of the water concentration in these solvents had little effect on enzyme flexibility. "Furthermore, the solvents themselves display a variety of freezing points down to below minus 100°C and dynamic behaviour is not affected by the solvent freezing. We expect that further investigation of these phenomena will give us information on the role water plays in enzyme structure and flexibility," he said. "An interesting consequence of these observations is that we should perhaps not be too quick to dismiss the idea of life at sub-zero temperatures. If enzymes can function in mixtures of organic solvents and water at minus 100°C, what is the barrier to life at these temperatures (albeit at a very slow tempo)? "We see a knowledge of enzyme dynamics as being as vital as a knowledge of structure and mechanism in understanding enzymes. The aim of our research is to increase our understanding of the role of dynamics in enzyme activity." Professor Daniel said that from a biotechnological perspective, enzyme engineering had enormous potential. "An understanding of how flexibility affects the action of the enzyme at the molecular level will enable us to design enzymes more effectively. "An increased understanding of enzymes could also have applications in other fields, such as medicine; for example, since most antibiotics act by interacting with enzymes to block their catalytic action, such an understanding could facilitate antibiotic design," he said. For further information, contact Professor Roy Daniel, Thermophile Research
Group, Department of Biological Sciences, University of Waikato Tel: (07) 838
4213Fax: (07) 8384324 Email: r.daniel@waikato.ac.nz Address: Private
Bag 3105, Hamilton
Volcanic glass helps track climate changeGeologists Dr Phil Shane, from Auckland University, and Dr Neil Ingraham, from the National Science Foundation in the United States, are probing the traces of ancient volcanic eruptions to find out how New Zealand's climate has changed over tens of thousands of years. The Marsden-funded research uses glass from volcanic eruptions known as tephra to help track the isotopic composition of ancient rainwater. "Tephra erupts from volcanoes in an anhydrous 'dry' state, and is dispersed widely by winds," said Dr Shane. "After settling on the ground the tephra layer is gradually buried by the development of soil, becoming hydrated by rain filtering into the soil. After one or two thousand years, the glass becomes fully hydrated and the water is 'trapped'. "This provides us with a record of the climate at the time, as the ratios of the oxygen isotopes (18O:16 O) and the hydrogen isotopes (deuterium:hydrogen) in water are sensitive to temperature and to the volume of ice accumulated on land," he explained. The central North Island proved an ideal place to investigate the use of tephra as a record of ancient rainfall. The Taupo Volcanic Zone has been the focus of numerous large eruptions that have been dated by radiocarbon methods. The research examined the ratio of hydrogen isotopes in large outcrops of tephra from well-known eruptions in the area. The relatively recent (in geological terms) 1800-year-old Taupo tephra revealed an isotope composition similar to the present day surface waters. "This fits in with other climate records that suggest only small-scale climate changes in the last 1000-2000 years," he said. "However, the 22,600-year-old Kawakawa tephra told us a different story. Here we saw a significantly different isotopic signal, consistent with global climate being significantly colder at that time. "We also examined outcrops containing several tephra beds of various ages. Each tephra displayed a unique isotopic ratio reflecting rainfall soon after the tephra was deposited." Geologists worldwide are working to decipher ancient climatic records in an attempt to document changes on the scale of hundreds and thousands of years. "The Taupo tephra deposits are a previously unexamined record of ancient climate in a temperate, terrestrial environment. For some time, deep-sea sediments and ice cores have been used to look at ancient climate. We now have a valuable new source of information," said Dr Shane. "Scientists and the public are increasingly concerned about climate change andthe impact it may have on society in the future. To understand changes that are taking place today, we need to place them in a long term context," Dr Shane concluded. For further information, contact Dr Phil Shane at the Department
of Geology, University of Auckland, Tel: (09) 373 7599 ext 7083 Fax: (09) 373
7435 Email: pa.shane@auckland.ac.nz Address: Private Bag 92019, Auckland
Roses are red, but could they be blue?
Pioneering Marsden-funded research into the relationship between pigment composition and flower colour could make a blue rose or a yellow sweet pea a reality. Such knowledge would be of enormous value to plant breeders and genetic engineers interested in changing flower colour to produce novel variants. Dr Ken Markham of Industrial Research is leading the work, in collaboration with colleagues Dr Kevin Gould from the University of Auckland, and Dr Chris Winefield from Crop & Food Research. Floral pigments fall broadly into two categories. They are the fat-soluble carotenoids that commonly produce yellows and oranges, and the water-soluble flavonoids (commonly anthocyanins), which produce a full range of colours from yellow through red to purple and black. "Being water-soluble, these flavonoid pigments are found in the cell vacuoles, cavities in the cell which contain fluid. We've always thought the mix of flavonoids in the vacuole determined the petal colour," Dr Markham said. "We recognise that factors such as pH, pigment concentration and interaction with other molecules (co-pigments) in the vacuole also influence this colour. "However, our research has shown that nature can be much more complicated than that. "In the commercially popular purple lisianthus flower, the inner region of the petal is much deeper in colour than the outer region. Optical microscopy studies revealed that this is due to the presence of intensely coloured inclusions containing anthocyanins, within the cell vacuoles. These AVIs (anthocyanic vacuolar inclusions) are absent or minimal in the rest of the petal, where the anthocyanin pigments are mainly in vacuolar solution. "AVIs have not been reported before and the effects of their presence appear to beto concentrate and stabilise colour, and to produce a blue shift in that colour," he said. "We isolated lisianthus AVIs by dissolving the surrounding cell wall and membranes, and found them to be remarkably stable. The pigments were bound tightly to what proved to be a protein complex. Intriguingly, of all the anthocyanins and co-pigments in the vacuole, only specific anthocyanin types were bound. The others remained in the vacuolar solution and contributed relatively little to the colour due to interaction with water. Another important aspect of the work involved investigating how 'colourless' flavonoids, such as flavonol glycosides, make flower petals yellow. "Microscopy on petal sections of a sweet pea relative, Lathyrus chrysanthus, and of white lisianthus, which is yellow at the base of the petal, gave us startling new insights into the location of the colourless flavonol glycosides. "We saw the glycosides not only in the cell vacuoles where they were expected, but also within the cell walls and in the cytoplasm which surrounds the vacuole," Dr Markham said. "In lisianthus, the cytoplasm-located flavonol glycosides were seen only in the yellowish inner region of the petal. In the completely yellow Lathyrus petal, they were found throughout. "By isolating and analysing cytoplasmic tissue we confirmed the presence of flavonoids in the cytoplasm. Then by using in vitro model systems to reproduce this colour, we concluded that the binding of 'colourless' flavonol glycosides to cytoplasmic protein produces the observed petal yellowing," Dr Markham said. "It is clear that the newly discovered phenomenon of protein binding, within AVIs or within the cell cytoplasm, has a dramatic effect on flower colour. Colour intensification, stability and a blue colour shift are all shown to result from such interactions. "The whole AVI phenomenon, now observed in other flowers, such as the carnation and the camellia, has relevance well beyond the manipulation of flower colour," he said. "The nature and chemistry of the binding reaction for example, have potential application in the stabilisation of natural dyes and colourants for industrial, and food and beverage uses." . For further information, contact Dr Ken Markham at Industrial Research LimitedTel: (04) 569 0577 Fax: (04) 569 0055 Email: k.markham@irl.cri.nz Address: P.O. Box 31310, Lower Hutt Theory gives stronger roots to the tree of life
Biologists now have powerful newtools for reconstructing the tree of life, thanks to a novel mathematical theory for combining evolutionary relationships. The theory has been developed by Marsden researchers Associate Professor Mike Steel and Dr Charles Semple at the University of Canterbury's Biomathematics Research Centre, together with mathematicians in Germany and Canada. Their results describe how trees that show the evolution of groups of species can be combined into an evolutionary "supertree" for all the species under study. Until now only ad-hoc methods have been available for this problem. The figure illustrates some of the main ideas. Each of the four trees at the top shows how groups of three present-day species are believed to have evolved from ancestral species. Each of these four trees is constructed by statistically analysing DNA sequences in each of the species and, from the differences, working out how long ago the species diverged. Dr Semple said the big question was whether these trees could together form a supertree. And if so, did they fit together in just one way? "In this example, the first two 3-species trees fit together in only one way they 'force' the 4-species tree in the middle left of the figure. That is, each of the first two trees 'sits inside' this larger tree, yet none of the other possible trees of these four species does this. "Similarly the last two trees on the top layer force the 4-species tree in the middle-right. As for the two forced trees in the middle layer, these in turn force the 6-species supertree at the bottom. So this is the only tree (among 945 possibilities) that accommodates all the four trees at the top of the figure. "If you believe those four 3-species trees are true, and the evolution of species is described by a tree, then you are forced to accept the 6-species tree," he said. While this is just an example, the group has developed techniques for combining more complicated trees into supertrees. "This has led to new techniques and results in a series of papers in mathematics, computer science and biology journals," Associate Professor Steel said. "So while some biologists can build up an evolutionary tree for their particular favourite group, others can start to piece together these trees for different groups ofspecies, to gain a larger and more accurate picture of the way species evolved."
For further information, contact Associate Professor Mike Steel, Biomathematics Research Centre, University of Canterbury Tel: (03) 364 2987 ext 7688 Fax: (03) 364 2587 Email: m.steel@math.canterbury.ac.nz http://web.math.canterbury.ac.nz/~mathmas/ Address: Private Bag 4800, Christchurch Probing the secret life of albino pollen
Mutants with white pollen in both Californian poppy and lavatera were the subject of a Marsden-funded project investigating the role pigments play in pollen biology. Most flowering plants have yellow to orange pollen resulting from various combinations of flavonoid and/or carotenoid pigments. While the chemistry of pollen pigments has been relatively well investigated, little is known about the physiological role colouring plays in pollen biology. As part of the first phase of their project, researchers Professor Tony Conner, Dr Carolyn Lister, from Crop & Food Research, and PhD student Angela Wakelin studied the genetics and chemistry of the white lavatera and poppy pollen mutations. "These mutants are highly unusual because they are also very fertile. Usually colour-free pollen is infertile, severely limiting previous research on the biological role of pollen pigmentation," Professor Conner said. In the wild, both the petals and pollen of Californian poppies are almost entirely a vivid orange. Lavatera, a shrubby plant with trumpet shaped flowers, usually has dark pink petals and pollen. In both flowers the presence or absence of pigments is inherited in patterns consistent with control by a single gene. And for both lavatera and Californian poppy an absence of pigments in the pollen was accompanied by an absence of pigment in the petals as well. "We analysed pollen and petals from both flowers and both mutant and non-mutant strains for flavonoid and carotenoid composition. Our aim was to see whether variations were associated with an absence of pigment," he said. "For the Californian poppy, the presence of carotenoids varied sharply between mutant and non-mutant varieties. In the orange wild-type, carotenoids were present in large quantities, while in the mutant they were barely detectable in the petals and absent altogether from the pollen. We found no difference in flavonoid content between the orange and white varieties." The team found that in the case of lavatera, there was a different pattern. Carotenoid levels were not one of the distinguishing differences between mutant and non-mutant lavatera, with carotenoids absent in all the samples of pollen and petals. "However chemical analyses have shown significant differences in the total flavonoid content between the dark pink and the white flowers, mainly due to variations in anthocyanin content," said Dr Lister. "The mutations identified in Californian poppy and lavatera therefore offer alternative experimental systems for investigating the biological role of pollen pigments. "One mutant was deficient in carotenoids and the other in anthocyanins, each representing a different major class of plant pigments." With this background on the genetics and chemistry of the mutants, the next research phase involved determining the reproductive success of the mutant pollen. Experiments comparing the fertility of the pigment-deficient and pigmented pollen confirmed that the loss of pollen pigments didn't lead to any loss of reproductive fitness in either species. "We're now into the final phase of our research. This work involves pollen competition experiments to determine if pollen pigments play a role in protecting a plant from the mutagenic effects of UV light or in providing anti-oxidants against stress."
For further information, contact Professor Tony Conner or Dr Carolyn Lister at the New Zealand Institute for Crop & Food Research, Lincoln Tel: (03) 325 6400 Fax: (03) 325 2074 Email: connert@crop.cri.nz or listerc@crop.cri.nz Address: Private Bag 4704, Christchurch Marsden Fund Update is published quarterly by the Marsden Fund and is available free on request. Editor: Redmer Yska Email: red.yska@clear.net.nz | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||
