Collaboration drives innovation. It is at the interface of different disciplines that science can lead to some intriguing outcomes and solutions to problems

Only about 10% of the energy captured by plants allocated to biomass production with the remainder being used in 'futile cycles' and high-cost cellular processes, such as transport of nutrients and respiration. Theoretical considerations lead to the conclusion that small gains in energy redistribution could lead to marked positive impacts on biomass accumulation and yield. Such gains might be achievable the cell, tissue and whole-plant levels, with respiration being a prime target. Selection of parental breeding materials for increased EUE seems a sensible way to fast-track the incorporation of such knowledge into various field crops. Technology to enable the project through high-throughput screening of respiration and growth has been developed by PEB researchers. We can show that high-throughput screening methodology can be used to identify genotypes, loci and markers usable in breeding programs. Screening will help identify genotypes with (i) lower rates of leaf respiratory CO2 released per unit growth; (ii) optimized levels of sugars, organic and amino acids for growth; and, (iii) increased biomass at anthesis. Our expertise can allow quantification of linkages between respiration, EUE, growth, biomass production, and yield, thus leading to trait and gene identification, and the development of genotyping and physiological modelling tools for gene stacking and crop improvement in general.

Contact Owen Atkin

Gamma aminobutyric acid (GABA), a well-known neurotransmitter in animals, and its receptors in humans are targets for numerous pharmaceuticals. In plants it is known as a key C:N metabolite that increases in concentration in plant tissues in response to stress. GABA can affect plant growth or guide pollen tubes through female tissue affecting fertilisation and seed set. We have identified the first GABA receptor/ion channel in plants, analogous to the GABA gated chloride channel in animals. GABA therefore can act as a signal in plants by affecting the membrane voltage similar to its mode of action in animals, but acting via very different proteins. We have identified specific residues in the receptor protein family that are required for GABA interaction. The ALMT family is widespread in plants, with known key physiological roles, including stomatal regulation, aluminium tolerance, hypocotyl growth, guard cell regulation, and pollen tube growth. The fact that GABA can modify receptor activity creates opportunities to manipulate stress responses and link with membrane signalling and metabolic processes. We are looking into increasing tolerance to alkaline and anoxic soils, salinity, and to water and heat stress through altered stomatal regulation and floret fertility, as well as biotrophic interactions (mycorrhiza and N fixation) and long-distance electrical signalling. The set target is to modulate stress response signalling to maximise yield under selected environmental stresses. This could be achieved using GABA agonists and antagonists or by precision engineering of the receptors. The identification of specific GABA receptor alleles leading to improved stress responses could be used in the selection of better parental materials in breeding.

Contact Matt Gilliham

Drought tolerance in Arabidopsis and wheat can be achieved by inhibiting the activity of the protein SAL1, leading to increased levels of the signalling metabolite PAP, that modulates stress response pathways. Arabidopsis SAL1 mutants survive drought longer than wild-type plants. Knockouts of two of the SAL1 homeoforms in wheat increase viability in pot-based drought experiments and exogenous application of PAP can close stomata in barley. SAL1 mutants have potential as a means to modulate drought effects by leading to a less conservative response and thus leading to maintenance of full turgor and higher water potential under stress and thus more sustained photoassimilation and productivity. Various GM and non GM approaches can be used to generate the required changes to the SAL1 alleles, which are expected to lead to plants with various levels of drought responses, as required. Evaluating the practical and commercial potential for licensing of new germplasm by breeders and breeding companies is now possible.

Contact Barry Pogson

Nutrient availability, particular in the case of phosphate, is highly variable across soil types, seasons and rainfall patterns. Fertiliser use constitutes a major cost factor in modern agriculture. This project aims to explore plant signalling networks that sense nutrient availability in the soil and change resource allocation within the plant in order to enhance the roots’ capacity to forage for nutrients and to ensure continuous growth. Greater resource allocation to roots has been identified as the major determinant of nutrient uptake efficiency in barley, rice and wheat. Our work on phosphorus uptake efficiency in wheat demonstrates that efficient transport and conversion of inorganic phosphate into organophosphates is critical. In Arabidopsis, meta-analysis identified specific root cells (termed “gatekeepers”) enriched for transcripts of putative key regulators of the P starvation response, some of which are part of protein kinase networks, transporters critical for leaf P homeostasis, and factors involved in cell-wall expansion and DNA methylation, all related to nutrient uptake and enhanced shoot-to-root resource allocation. The opportunity now exists to modify these factors in crop plants to determine the impact on P uptake and PUE traits.

Contact Jim Whelan

Salinity in its different guises affects a high proportion of cropping areas worldwide, severely reducing productivity. Plans are underway to conduct precision mapping of soil in breeders’ plots together with aerial mapping to be able to quantify their combined effects on yield and thus enable the group to quantify the benefit of a given tolerance trait. This missing part of the puzzle will be combined with the group’s expertise in plant proteomics, metabolomics, transcriptomics, biochemistry and transport biology to deliver a complete trait package.

We are working at the forefront of discovery on various field crops and identified a number of key genes providing different mechanisms of salinity tolerance (tissue tolerance, ion exclusion, osmotolerance, and water channels), having already successfully demonstrated the enhanced tolerance conferred to durum wheat by the gene Nax2. Ongoing work aims at identifying the best gene combinations to deal with specific soil toxicities affecting large cropping areas, e.g. soil sodicity (a complex combination of several chemical and physical constraints). Other types of saline soils are similarly complex, with stresses being imposed on the plant by a combination of ionic composition, moisture-dependent ionic strength, low moisture, and a high content of toxic ions like aluminium, manganese and iron.

We can fast-track adapted genotypes carrying the desired gene combinations by collaborating with breeding companies and other partners on proof-of-concept and validation field trials.

Contact Matt Gilliham

The use of hybrid crop varieties is increasing because of their attractive agronomic traits - they tend to grow faster and yield better (hybrid vigour), and they are generally more robust to biotic and abiotic environmental challenges. Gains in productivity are commonly 15-20% and often higher. However, producing hybrids in self-pollinating crops (and that’s most field-grown crops) is highly challenging. The female (seed) parent must be prevented from self-pollinating by physically, chemically or genetically ablating the male organs or the pollen they produce. A widely-used genetic method is to employ a mitochondrial gene that induces pollen abortion, so-called cytoplasmic male sterility (CMS). However, being maternally inherited (in most plants), the CMS gene will be transmitted to the hybrid progeny. To ensure the hybrids are fertile, breeders use a male parent for the cross that carries a nuclear Rf gene that prevents expression of the mitochondrial CMS gene. Rf proteins are imported into mitochondria, bind the CMS transcript and prevent its translation. The high value of hybrid crops makes effective Rf genes highly sought after. Almost all known Rf proteins are pentatricopeptide repeat (PPR) proteins. The ARC Centre of Excellence in Plant Energy Biology’s research has provided new ways of identifying natural Rf genes and predicting their activity. It has also developed the capacity to construct genetically engineered Rf genes that could target any mitochondrial sequence. These capabilities are valuable to plant breeding companies keen to develop new hybrid varieties, particularly in crops where such hybrids have been difficult to create.

Contact Ian Small