2011 Annual Report
1a.Objectives (from AD-416)
Determine the molecular mechanisms by which plants perceive and respond to developmental, biotic and abiotic signals throughout the life cycle to enhance the quality and production efficiency of agriculturally important crops.
1b.Approach (from AD-416)
A combination of modern molecular, genetic, genomic, proteomic and bioinformatic approaches will be used to address this multifaceted problem. Particular emphasis will be placed on identifying signaling components, regulatory genes and transcriptional networks involved in controlling plant responses to developmental, biotic and abiotic signals. Genes that respond to light under control of the phytochrome photosensory system will be identified and the regulatory mechanisms defined. Genes involved in regulating the circadian clock will be identified and functionally defined. Genes controlling vegetative and reproductive development will be identified and characterized. Plant hormone function in mediating growth and developmental responses will be explored. Genes involved in plant responses to biotic and abiotic challenges will be identified and characterized. On an ongoing basis, cutting-edge strategies and technologies in areas such as targeted reverse-genetic gene disruption, high-density microarray analysis, and biocomputational approaches, will be assimilated and will be identified and characterized.
ARS scientists in collaboration with scientists of UC Berkeley increased our knowledge of how plant genes function. They showed that the Anaphase-Promoting Complex (APC), previously known to have a role in protein degradation, also regulates transcription of a cell cycle gene, and that this regulation, which is mediated by microRNAs, is important for pollen development. They published a comprehensive analysis of CLV3-related CLE polypeptide signaling gene expression and over-expression activity in Arabidopsis vegetative and reproductive development. This work indicated that many plant developmental and/or physiological processes may be regulated by CLE-mediated intercellular signaling. Scientists also discovered that a number of diverse signaling pathways appear to converge on the Phytochrome-Interacting Factor (PIF) family of bHLH transcription factors as intermediates in the transduction process. The list of pathways includes ethylene signaling, thus expanding the scope of the concept further. Another group developed maize mutants that accelerate flowering time and shorten plant stature, demonstrating that the circadian clock regulates these important aspects of maize development. They established that the rapid flowering of Arabidopsis plants induced by high temperature is a response specifically to the high temperature during the last half of the day. These findings are relevant to the effect of global climate change on plant development. Another group identified a gene that regulates glucose levels in maize cell walls. Plants carrying a mutation in the gene have higher glucose in adult leaves and improved saccharification, which makes a better lignocellulosic biofuel. Finally, ARS scientists discovered that disease resistance loci in the Solanaceous species, such as potato and tomato, are targeted by small RNAs. The small RNAs modulate the level of expression of these expanded gene families.