It can be said that the major trait of a plant is GROWTH. How is growth controlled? From within (i.e., the plant's own genes) or from outside (the plant's nutritional, climatic and disease environment)? Clearly the answers come from the COMBINATION of internal and external factors, and their complex interactions.
Plant growth has multiple phases. Embryos develop after successful fertilisation, and seeds develop around them to provide nutrients for the growth of the emerging seedling. Seedlings progress from a vegetative growth into a regenerative phase, leading to renewed generation of gametes (ova and pollen) that combine to form new embryos.
All phases of plant growth are controlled by the genome, its internal complex 'read-out', and the constant interaction with the environment.
Whilst most of science focus has been on annual crop plants (soybean, pea, corn, wheat, canola, etc), it must be remembered that many plants live longer than one season! Thus perennials (such as most forage legumes) and trees (such as Pongamia and acacia) display modification of regulatory circuits seen in annuals.
The new CILR sees the opportunity of increased analysis into plants beyond the narrow focus on the model plant Arabidopsis. Whilst it is not denied that the three decades of intensive genetic and biochemical research into the weedy crucifer have propelled plant science forward, we must recognise the need for TRANSLATIONAL BIOLOGY. That is, knowledge from model systems, whether Arabidopsis or the legumes, Lotus japonicus and Medicago truncatula, is applied to food and fuel application.
Legumes are a major plant group (over 17,000 species) that contribute to global food and feed supply as well as providing wood, oil and pharmaceuticals. Prominent examples are soybean, pea, common bean, cloves, groundnut (peanut), chickpea, the biofuel tree Pongamia, lupins, Acacia trees (wattle), Wisteria, medics, clovers and cassias. Together with cereals, legumes provide the majority of global food? Legumes can assimilate (or "fix") atmospheric nitrogen into their own cells due to a relationship with beneficial soil bacteria known as rhizobia. Rhizobia induce legume roots to form tiny new root organs called "root nodules." The bacteria live harmoniously inside these nodules and provide the plant with useable nitrogen it can convert into proteins, nucleic acids and general metabolites.
Legumes have a wide range of applications. They are a natural fertiliser and soil improver, and therefore can contribute to preserving environmental quality and agricultural sustainability. Legumes are an important food source for both humans and animals. Their seeds are high in protein and contain various nutriceuticals (including phytoestrogens, lecitin, and anti-oxidants). Some legumes produce valuable starches, while others contain cholesterol-free vegetable oils. Biodiesel made from legume seeds provides a green alternative to fossil fuels. The value of legume crop production worldwide exceeds A$200 billion each year.
Our research provides fundamental insights into understanding the biology of legumes so that we can improve on how they are utilised. A better understanding of input traits relating to phosphorus-, nitrogen- and water-use by plants can lead to enhanced plant growth, which originates from multiple growth points called meristems. The ultimate outcome of effective plant growth management is improved output traits. Useful output traits include improved environmental adaptation, increased protein production and oil synthesis for food and biofuels.
Legume biology provides a unique opportunity for discovery. The CILR's research focus is to understand meristems (regions of actively dividing cells giving rise to new tissues). The Rhizobium-induced nodule meristem is exclusive to legumes (bar the exception of Parasponia). This relationship allows us to test hypotheses concerning the induction, maintenance and regulation of plant stem-cell populations maintained in meristems. Specifically, regulation of the proliferation of the nodule meristem was shown by CILR investigators to be controlled by systemic inter-organ communication. We have since expanded this groundbreaking concept to find it helps explain lateral branching in pea and soybean as well as the regulation of lateral root growth in the model legumes Medicago truncatula and Lotus japonicus.
The global need for renewable protein and plant oil resources has accelerated progress in legume gene discovery and DNA sequencing on an international level. Much of CILR's research focuses on two model legume species Lotus japonicus and Medicago truncatula because they are relatively easy to study. The Lotus and Medicago genomes are nearly sequenced and useable versions have been published in 2011. The soybean genome was made available in late 2010. Lotus and Medicago have small diploid genomes, fast generation times and produce numerous small seeds. They are self-fertilising and can be grown from cell culture. Gene transfer and mutagenesis are efficient.
By researching model legumes our investigators can extend their findings to understand important crop legumes such pea, beans, lentil, lupin, clovers, and soybean as well as the biofuel legume tree Pongamia (Millettia) pinnata.