Project description:Pollen development is one of the most heat-sensitive developmental stages in a wide range of crops. Our longer-term goal is to understand the mechanism how starch metabolism in maturing pollen grains of the Solanaceae family contributes to maintaining higher pollen quality under heat-stress conditions. The specific aim of the suggested proposal is to characterize N. sylvestris WT and mutant (starch-deficient) transcriptomes during microgametogenesis under ambient and heat-stress conditions. Expression profiles of maturing microspores derived from flower buds at developmental stage of 4 to 2 days before flower opening will be obtained. Pollen was derived from WT and mutant plants exposed to either ambient or heat-stress conditions (exposing the plants to 45oC for 2.5 hours). Keywords: Loop design
Project description:Previous analyses suggested that the Nicotiana sylvestris CMSII mutant carried a large deletion in its mitochondrial genome. Here, we show by cosmid mapping that the deletion is 60 kb in length and contains several mitochondrial genes or ORFs, including the complex I nad7 gene. However, due to the presence of large duplications in the progenitor mitochondrial genome, the only unique gene that appears to be deleted is nad7. RNA gel blot data confirm the absence of nad7 expression, strongly suggesting that the molecular basis for the CMSII abnormal phenotype, poor growth and male sterility, is the altered complex I structure. The CMSII mitochondrial genome appears to consist essentially of one of two subgenomes resulting from recombination between direct short repeats. In the progenitor mitochondrial genome both recombination products are detected by PCR and, reciprocally, the parental fragments are detected at the substoichiometric level in the mutant. The CMSII mtDNA organization has been maintained through six sexual generations.