Molecular Analysis of Sink Limited Soybeans

Soybean plants that do not produce a sink, such as depodded or male sterile plants, exhibit physiological and morphological changes during the reproductive stages, including increased levels of nitrogen and starch in the leaves and a delayed senescence. To identify transcriptional changes that occur in leaves of sink-limited plants, we used RNAseq to compare gene expression levels in trifoliate leaves from depodded and ms6 male sterile plants and control plants. In sink-limited tissues, we observed a deferral of the expression of senescence-associated genes and a continued high expression of genes associated with the maturity phase of leaf development. We identified GO-terms associated with growth and development and storage protein in sink limited tissues. We also identified that the bHLH. ARFs, and SBP transcription factors were expressed in sink limited tissues while the senescing control leaves expressed WRKY and NAC transcription factors. We identified genes that were not expressed during normal leaf development but highly expressed in sink-limited plants, including the D4 “non-yellowing” gene. These changes highlighted several metabolic pathways that were involved in distinct modes of resource parttioning in the “stay green” leaves.