A guardian of grasses

Anoop Sindhu and colleagues report on a gene that may have played a key role in the evolution of grasses. The gene, Hm1, provides resistance against Cochliobolus carbonum race 1 (CCR1), a fungus that is capable of attacking and killing corn at any stage of its development (images of CCR1 infection). While CCR1 is only known to affect corn, the gene Hm1 and its relatives are present throughout the grass family, but are absent from other lineages.

CCR1 is only known as a disease in Zea mays, but the Hm1 family of genes throughout the grass family. Sindhu and colleagues silenced the corresponding gene in barley. This resulted in barley that was susceptible to CCR1. The fungus is able to invade susceptible grasses through the production of Helminthosporium carbonum* (HC) toxin. The ability of Hm1 and related genes to resist CCR1 comes from an enzyme known as HC-toxin reductase (HCTR), which detoxifies HCTR.

A phylogenetic analysis of the Hm1-gene family showed that they were monophyletic - they all shared a common ancestor. Since it is present throughout the grass family, but is absent from all other groups of plants, it appears that the gene shares its origin with the grass family. This lead the authors to conclude that:

The maintenance of HCTR gene function in maize and barley, coupled with the unique phylogenetic position of the Hm1 gene (with no closely related orthologs in eudicots), suggests that Hm1 may have played a critical role in the evolution of most of our cereal crops. Given the devastating potential of CCR1 to kill susceptible corn, it is likely that this fungus or its ancestral form would have threatened the existence of grasses, or at least severely constrained their geographical distribution, had Hm1 not evolved to detoxify HC toxin. Thus, it seems likely that Hm1 served as a guardian of the grass family, allowing it to survive, thrive, and evolve into crops that feed the world.

*Helminthosporium carbonum is the asexual form of Cochliobolus carbonum. Since fungi are classified on the basis of their sexual structure, fungi whose fruiting bodies are unknown often end up being described as distinct species.

Sindhu, A., Chintamanani, S., Brandt, A.S., Zanis, M., Scofield, S.R., Johal, G.S. (2008). A guardian of grasses: Specific origin and conservation of a unique disease-resistance gene in the grass lineage. Proceeding of the National Academy of Sciences USA, 105(5), 1762-1767. DOI: 10.1073/pnas.0711406105 Open Access

Onions without tears

Using gene silencing, researchers in New Zealand's Crop and Food research institute were able to make onions that don't make you cry when you cut them.

Source: PhysOrg.com

Eat your carrots - you need the calcium

Food science tends to focus on improving the nutritional quality of foods, but rarely does it look at how these "improved" foods affect human (or animal) health. A group of researchers from Texas A&M University and Baylor College of Medicine looked at whether enriched calcium in foods was actually used by the body. They had previously engineered carrots which had twice the normal level of calcium. In a paper published in the Proceeding of the National Academy of Sciences USA, they looked at the fate of this calcium in the body. By using labelled calcium they were able to observe its eventual fate. Their conclusion:

In a cross-over study of 15 male and 15 female adults, we found that when people were fed sCAX1 and control carrots, total calcium absorption per 100 g of carrots was 41% ± 2% higher in sCAX1 carrots. Both the mice and human feeding studies demonstrate increased calcium absorption from sCAX1-expressing carrots compared with controls. These results demonstrate an alternative means of fortifying vegetables with bioavailable calcium.

Morris,Jay, Hawthorne,Keli M., Hotze, Tim, Abrams Steven A., and Hirschi*, Kendal D. 2008. Nutritional impact of elevated calcium transport activity in carrots. Proceeding of the National Academy of Sciences USA 105(5):1431-1435 DOI:10.1073/pnas.0709005105

Is it really organic?

It can be difficult to determine whether something is really organic. How can you tell if a producer is calling food organic that isn't? While most persticides are likely to leave residues that could be tested for, fertilisers are more difficult to detect. One possibility is to look for differences in the ratios of stable isotopes of nitrogen - nitrogen. Spanish scientists Francisco del Amora, Joaquín Navarroa and Pedro Aparicio decided to see if they could tell the difference between organic and conventionally grown crops on the basis of nitrogen isotope ratios. They concluded that it was possible to detect fertiliser use.

Agencies for organic farming certification require techniques to verify the organic nature of the N fertilizers applied to crops. Results show that significant differences have been found between organic and not fully organic practices. Thus, this study demonstrates that with N-isotopic techniques it is possible to discriminate the use of chemical fertilizers in the organic production of sweet peppers with respect to strictly nonorganic crops. Further studies including the effects of different soils characteristics, climate, and biotic or abiotic stress could be useful in determining the proper interval of ¹⁵N/¹⁴N ratio to exclude nonorganic fertilization practices.

del Amora,F.M., Navarroa J., and Aparicio, P.M. 2008. Isotopic Discrimination as a Tool for Organic Farming Certification in Sweet Pepper.

Internationally Important Algal Habitats

Fifteen locations in Britain have been identified as internationally important based on their algal flora.

Among the 15 locations listed is a freshwater area in Cornwall near St. Just that has 100 species of algae, two of which are classified as rare. Another important area is a coastal site at Lundy Island off Devon with 300 species of algae.

Source: PhysOrg.com

Immune systems in plants

In a review article due to be published in the journal Developmental & Comparative Immunology John M. McDowell and Stacey A. Simona looked at "plant-pathogen interface" and found notable similarities and differences between the molecular immune responses of plants and (metazoan) animals. They concluded that

It now seems clear that plants and animals have independently adopted many of the same protein modules for immune surveillance. Many interesting mechanistic and evolutionary parallels are evident upon comparison of immune surveillance in plants and animals, and we look forward to productive, “cross-species” dialog between animal and plant immunologists in the years to come.

McDowell, J.M. and Simona, S.A. 2008. Molecular diversity at the plant–pathogen interface. Developmental & Comparative Immunology doi:10.1016/j.dci.2007.11.005

Insecticidal compounds in plants

Several members of three plants families - the Rubiaceae, Violaceae and Cucurbitaceae- produce cyclotides, cyclic mini-peptides made up of 28-37 amino acids arranged in a circular configuration. These compounds are very stable and have attracted the attention of pharmaceutical companies. Because these peptides lack free amino and carboxyl ends, they cannot be broken down by proteases. The compounds appear to act primarily as insecticides. In an article published in the January 29 issue of PNAS, Barbara Barbeta and colleagues investigated the role of these compounds on the larvae of lepidopterans (butterflies and moths). The compounds damaged the cells of the midgut of Helicoverpa armigera larvae, which severely stunted their growth (image from Wikipedia; see license details).

Barbeta, B.L., Marshall, A.T., Gillon, A.D., Craik, D.J., and Anderson, M.A. 2008. Plant cyclotides disrupt epithelial cells in the midgut of lepidopteran larvae. Proceedings of the National Academy of Sciences USA 105(4):1221-1225 DOI:10.1073/pnas.0710338104

Tropical Plant Biology journal launched

Springer is launching a new journal Tropical Plant Biology. This first issue is due in March 2008. According to the press release, the journal will:

[R]eport on significant advances in all aspects of tropical plant biology as well as applications towards genetic diversity and crop improvement."

Tropical Plant Biology will cover the most rapidly advancing aspects of tropical plant biology including physiology, evolution, development, cellular and molecular biology, cytology, genetics, genomics, comparative genomics, genomic ecology and molecular breeding. It will publish articles of original research as well as review articles. Occasional special issues focused on a single tropical crop species or breakthrough will also be published. The information in this journal will guide efforts to increase the productivity and quality of tropical plants and preserve the world’s plant diversity.

The journal will be edited by Paul H. Moore of the International Consortium for Sugarcane Biotechnology and and Ray Ming of the Department of Plant Biology, University of Illinois at Urbana-Champaign, both of whom focus on tropical crops.

Plastid evolution

A forthcoming paper in the Annual Review of Plant Biology looks really interesting: Plastid Evolution. Written by Sven Gould, Ross Waller and Geoffrey McFadden of the University of Melbourne, it looks really promising. From the abstract:

We review the origins, integration, and functions of the different plastid types with special emphasis on their biochemical abilities, transfer of genes to the host, and the back supply of proteins to the endosymbiont.

Gould, S.B., Waller, R.F. and McFadden, G.I. 2008. Plastid Evolution. Annual Review of Plant Biology 59

Interactions between Bt crops and mycorrhizal fungi

In the February issue of Acta Agriculturae Scandinavica, Section B - Soil & Plant Science Liu Wenke and Du Lianfeng raise the question of whether Bt transgenic crops pose a threat to soil microorganisms, especially arbuscular mycorrhizal fungi. From the paper's abstract

Bt transgenic crops may affect AMF in many ways during their life with regard to the temporal-spatial relevance between the occurrence of Bt proteins and fungal symbiotic development of AMF. This may lead to an unwelcome surprise with regard to specific abundance and diversity of AMF when Bt transgenic crops are planted continuously. It is concluded that interactions between AMF and Bt transgenic crops at individual and community level are a new urgent soil ecological issue. Some evidence about Bt transgenic crop effects on AMF revealed by recent articles are summarized, and research prospects are highlighted in the paper.

Wenke, Liu and Du Lianfeng. 2008. Interactions between Bt transgenic crops and arbuscular mycorrhizal fungi: a new urgent issue of soil ecology in agroecosystems. Acta Agriculturae Scandinavica, Section B - Soil & Plant Science 58 (2) 187 - 192 DOI:10.1080/09064710701478339

Ecological Dimensions of Biofuels Conference

The Ecological Society of America is sponsoring a conference on the Ecological Dimensions of Biofuels in Washington DC on March 10. Registration for the conference closes February 21. The conference website frames the issue:

Production of fuels from plants and agricultural and forestry wastes can reduce both society’s dependence on fossil fuels and net emissions of atmospheric carbon dioxide, the major contributor to global warming. Expanded use of this bioenergy requires assuring that its production and consumption are truly sustainable. This conference will explore the ecological dimensions of biofuels production and will identify management strategies and research opportunities to ensure their sustainability.

Some of the best writing on this issue can be found at Mike Palmer’s blog Low-Impact, High-Diversity Biofuels. Mike Palmer is an ecology professor at Oklahoma State University.

Predicting plant invasions

In trying to identify potential invaders, most people tend to look for classic weeds. Species which mature quickly and produce large quantities of readily dispersed seed seem to be ideal candidates for invasion. However, actual studies of invasive species have shown them to be highly idiosyncratic - a non-native species that is invasive in one context may be benign in another context. In a paper published in the January issue of the Journal of Ecology, Angela Moles, Monica Gruber and Stephen Bonser have proposed a new framework for trying to identify potentially invasive plant species. [more]

Pitcher plant gives up its secret

Pitcher plants use digestive enzymes to break down insects and use them as a nitrogen source. In a paper published in the Journal of Proteome Research, Naoya Hatano and Tatsuro Hamada used proteomic analysis to identify the full suite of enzymes that are present in pitcher fluid of Nepenthes alata. In addition to enzymes which break down proteins (which had been previously isolated) they found several proteins believed to inhibit bacterial growth.

Source: PhysOrg.com

Algae for food, fertiliser and fuel

A profile of the Laboratory for Algae Research & Biotechnology (LARB) at Arizona State University’s Polytechnic Campus talks about the potential for algae for use as food, fertiliser and biofuel. Algae is being seen as a potential biofuel that does not compete with food for agricultural land. It can also be grown using agricultural wastes as a nitrogen source.

It sounds like a really interesting idea. Hopefully it won't be a cure that's worse than the disease...

Source: PhysOrg.com

Biocontrol for Australian invasive?

Boneseed (Chrysanthemoides monilifera subsp. monilifera), one of Australia's "20 Weeds of National Significance" is the target of a biocontrol study using a rust fungus, Endophyllum osteospermi, that attacks it in its native range in southern Africa. The study is a collaboration between CSIRO in Australia and the Plant Protection Research Institute in Stellenbosch, South Africa.

Source: PhysOrg.com

Plant fungus affects sex ratios in parasitic wasp

From PhysOrg.com

The study, recently published in the Proceedings of the Royal Society B, focused on the fungus (Podosphaera plantaginis), the plant (Plantago lanceolata), the checkerspot caterpillar (Melitaea cinxia) and the parasitoid wasp (Cotesia melitaearum) that share habitat in Åland, Finland.

The fungal endophyte alters leaf chemistry in the host plant. This slows the growth rate in Melitaea cinxia caterpillars that feed of the plant. The parasitoid wasp lays its eggs on the caterpillar; like other parasitoids, the wasp larvae gradually consume the still-living host. When the female wasp lays her eggs on caterpillars feeding on Podosphaera plantaginis plants, she ends up producing twice as many female as male offspring. A skewed sex ratio improves the success of these wasps in the fragmented habitat in which they live.

Preserving Salem College's Herbarium

When Jennifer Cruse Sanders took over Salem College's Herbarium in 2005 it had been closed since 1980. In that time it collections - some dating back to the 1820s - had suffered from neglect and tobacco beetle attack. Now, with Cruse Sanders moving to a job at the Atlanta Botanical Gardens, and her student assistant, Kristian Jones graduating, there is concern about the future of the collection.

[David Bare, Winston-Salem Journal]

A remarkable new palm from Madagascar

As a result of its long isolation, Madagascar has unique biota. Although it is best known for its lemurs, Madagascar’s palm flora is both diverse and distinctive. In 1995 Dransfield and Beentje recognised 170 species of palms from Madagascar, 164 of which were found only in Madagascar. Since then another 7 species have been described, with another 20 apparently awaiting description. Most of these new species have been found in the eastern wet areas. The western part of the island is drier, and has a much less diverse palm flora. However, an entirely new genus has been discovered in the western dry region - one that is so large and distinctive that the BBC reports it can be seen in satellite images. A description of this new species, Tahina spectabilis was published in the January issue of the Botanical Journal of the Linnean Society.

Tahina, which means “blessed” or “to be protected” in Malagasy (and is also the name of the daughter of the Metz family, Anne-Tahina), is a remarkable tree. It is one of the largest palms in Madagascar, growing 10 m tall (20 m according to the BBC article) with stem diameter of 50 cm. It is also hapaxanthic - it reproduces just once in its lifetime and them dies. As a result of this, it puts all of its resources into flowering, producing a 4-m tall inflorescence. (You can see an image of it here.) [more...]

Baylor honours Steve Davis

Pepperdine plant ecologist Steve Davis received Baylor University's Robert Foster Cherry Award for Great Teaching. The $200,000 Cherry Award is the only national teaching award presented by a college or university. Having seen Davis speak, I can attest that he's an engaging speaker who really manages to convey ideas well. Although it was several years ago, I remember his talk (on chaparral fire ecology) vividly.

Mooney and Raven honoured

The Mexican Fundación BBVA Award for Scientific Research in Ecology and Conservation Biology went to Peter Raven (Missouri Botanical Garden) and Harold Mooney (Stanford), two on the most eminent plant biologists. Raven is systematist, while Mooney is known for his work in ecophysiology and global change biology.