2007 Annual Report 1a.Objectives (from AD-416) (1) To identify and analyze critical genes in sugar-hormone signaling and sugar metabolism during seed development, particularly in basal endosperm transfer cells, in maize. (2) To determine the bases for defective pollen biogenesis, including aberrations in sugar-starch metabolism, associated with heat stress and cytoplasmic male sterility in sorghum. 1b.Approach (from AD-416) Developmental profiles of various phytohormones in developing seeds of normal (wild type) and several carbohydrate mutants of known genetic bases in maize will be developed using high throughput chemical approaches, including gas chromatography / mass spectrometry (GC-MS). Contemporary genomic approaches will be used to identify genes that are critical to sugar - hormone cross-talk, especially those related to hormone metabolism, transcription factors and proteins that function as receptors and/or response factors. Such genes in developing seeds will be further analyzed in expression studies using both microarray and single gene approaches to dissect gene networks that may control normal seed development and sink strength, the two most critical components of crop yields. Gene discovery studies based on transcriptome and proteome approaches will be initiated to obtain a functional genomic profile of the Basal Endosperm Transfer Layer (BETL), a highly specialized cell layer known to be critical for transport and signaling functions in developing seeds. The emphasis in studying pollen biogenesis in sorghum is to understand the bases for defective biochemical, molecular and physiological processes (including aberrations in sugar-starch metabolism) associated with heat stress and cytoplasmic male sterility (CMS). Profiles of differentially expressed genes that characterize the expression of CMS, the restoration of male fertility and heat-induced pollen inviability will be obtained and analyzed through contemporary transcriptome and proteome technologies. 4.Accomplishments Title: Cytoplasmic Male Sterility in Sorghum Genes that apparently cause CMS have been identified, and molecular markers for genes that restore fertility, required for seed production, have been identified. The markers should enable plant breeders to efficiently move these genes into important sorghum lines for evaluations of the ease of use of the alternative sources of CMS. Single-gene conversion lines were constructed with the markers, and seed was forwarded to collaborating geneticists. A two-gene sporophytic restoration system for the IS1112C male-sterile line was recovered from sudangrass and characterized. Research addresses National Program 302, Plant Biological and Molecular Processes, Action Plan Component 2 - Biological Processes that Improve Crop Productivity and Quality, Problem Statement 2A: Understanding Growth and Development. Title: Effect of High temperature on Pollen Development in Sorghum Global climate change or global warming poses serious threat to plant reproductive stages. High temperature stress-induced male sterility and consequent reduced seed set is a critical problem in sorghum (Sorghum bicolor). Collaborative research with scientists at the University of Florida has shown greatly reduced sugar and starch levels in developing pollen that leads to reduced pollen germination. Gene expression studies have now shown greatly reduced levels of nearly half a dozen genes involved in sugar cleavage and utilization. Impairment of cell wall invertase mediated sucrose hydrolysis is one of the most serious problems under heat stress. Selection of cultivars or varieties that have higher levels of invertases may survive better under heat stress. These results are valuable to molecular breeders and/or biotechnologists who may want to engineer crop varieties for increased heat tolerance through manipulation of pollen-specific cell wall invertase gene. Research addresses National Program 302, Plant Biological and Molecular Processes, Action Plan Component 2. Biological Processes that Improve Crop Productivity and Quality, Problem Statement 2A: Understanding Growth and Development. 6.Technology Transfer Number of non-peer reviewed presentations and proceedings 2 Review Publications Tang, H.V., Pedersen, J.F., Chase, C.D., Pring, D.R. 2007. Fertility restoration of the sorghum A3 male-sterile cytoplasm through a sporophytic mechanism derived from sudangrass. Crop Science. 47:943-950.