The soluble receptors of abscisic acid (ABA) have been identified in Arabidopsis thaliana. The 14 proteins in this family, bearing the double name of PYRABACTIN RESISTANCE/PYRABACTIN-LIKE (PYR/PYL) or REGULATORY COMPONENTS OF ABA RECEPTOR (RCAR) (collectively referred to as PYR/PYL/RCAR), contain between 150 and 200 amino acids with homology to the steroidogenic acute regulatory-related lipid transfer (START) protein. Structural studies of these receptors have provided rich insights into the early mechanisms of ABA signaling. The binding of ABA to PYR/PYL/RCAR triggers the pathway by inducing structural changes in the receptors that allows them to sequester members of the clade A negative regulating protein phosphatase 2Cs (PP2Cs). This liberates the class III ABA-activated Snf1-related kinases (SnRK2s) to phosphorylate various targets. In guard cells, a specific SnRK2, OPEN STOMATA 1 (OST), stimulates H(2)O(2) production by NADPH oxidase respiratory burst oxidase protein F and inhibits potassium ion influx by the inward-rectifying channel KAT1. OST1, the kinase CPK23, the calcium-dependent kinase CPK21, and the counteracting PP2Cs modulate the slow anion channel SLAC1, a pathway that contributes to stomatal responses to diverse stimuli, including ABA and carbon dioxide. A minimal ABA response pathway that leads to activation of the SLAC1 homolog, SLAH3, and presumably stomatal closure has been reconstituted in vitro. The identification of the soluble receptors and core components of the ABA signaling pathway provides promising targets for crop design with higher resilience to water deficit while maintaining biomass.

The year 2009 marked a real turnaround in our understanding of the mode of abscisic acid (ABA) action. Nearly 25 years had elapsed since the first biochemical detection of ABA-binding proteins in the plasmalemma of Vicia guard cells was reported. This recent--and laudable--achievement is owed largely to the discovery of the soluble ABA receptors whose major interacting proteins happen to be some of the most well-established components of earliest steps in ABA signaling. These soluble receptors, with the double name of PYRABACTIN RESISTANCE (PYR) or REGULATORY COMPONENT OF ABA RECEPTOR (RCAR), are a family of Arabidopsis proteins of about 150-200 amino acids that share a conserved START domain. The ABA signal transduction circuitry under non-stress conditions is muted by the clade A protein phosphatases 2C (PP2C) (notably HAB1, ABI1, and ABI2). During the initial steps of ABA signaling, the binding of the hormone to the receptor induces a conformational change in the latter that allows it to sequester the PP2Cs. This excludes them from the negative regulation of the downstream ABA-activated kinases (OST1/SnRK2.6/SRK2E, SnRK2.2, and SnRK2.3), thus unleashing the pathway by freeing them to phosphorylate downstream targets that now include several b-ZIP transcription factors, ion channels (SLAC1, KAT1), and a NADPH oxidase (AtrbohF). The discovery of this family of soluble receptors and the rich insight already gained from structural studies of their complexes with different isoforms of ABA, PP2C, and the synthetic agonist pyrabactin lay the foundation towards rational design of chemical switches that can bolster drought hardiness in plants.

Myo-inositol metabolism plays a significant role in plant growth and development, and is also used as a precursor for many important metabolites, such as ascorbate, pinitol, and phytate. Phytate (inositol hexakisphosphate) is the major storage pool for phosphate in the seeds. It is utilized during seed germination and growth of the developing embryo. In addition, it is implicated in protection against oxidative stress. In the present study, a panel of chickpea accessions was used for an association analysis. Association analysis accounting for population structure and relative kinship identified alleles of a simple sequence repeat marker, NCPGR90, that are associated with both phytic acid content and drought tolerance. These alleles varied with respect to the dinucleotide CT repeats present within the marker. NCPGR90 located to the 5'UTR of chickpea myo-inositol monophosphatase gene (CaIMP) and showed transcript length variation in drought-tolerant and drought-susceptible accessions. CaIMP from a drought-tolerant accession with a smaller repeat was almost 2-fold upregulated as compared to a susceptible accession having a longer repeat, even under control non-stressed conditions. This study suggests an evolution of simple sequence repeat length variation in CaIMP, which might be regulating phytic acid levels to confer drought tolerance in natural populations of chickpea.

Genetic biofortification is a cost-effective strategy to address iron (Fe) and zinc (Zn) deficiencies prevalent worldwide. Being a rich and cheap protein source, chickpea, a food legume grown and consumed across the globe, is a good target for biofortification. Nineteen popular commercial cultivars of India were analysed for Fe and Zn content at four locations representing different agro-climatic zones to study the genotypic and genotype 9 environment interactions on Fe and Zn. Distribution of phytic acid (PA), an important anti-nutrient that chelates and reduces the mineral bioavailability, was also analysed. Influence of other agronomic traits like days to flowering, plant