Transcriptional profiling of mechanically and genetically sink‐limited soybeans

• Published in: Plant, cell and environment Vol. 40; no. 10; pp. 2307 - 2318
• Main Authors: Brown, Anne V., Hudson, Karen A.
• Format: Journal Article
• Language: English
• Published: United States Wiley Subscription Services, Inc 01.10.2017
• Subjects: auxins; Binding; binding proteins; biochemical pathways; Biomechanical Phenomena; Controlled conditions; depodded; expression profiling; Gene expression; Gene Expression Profiling; gene expression regulation; Gene Expression Regulation, Plant; Gene Ontology; Genes; Genes, Plant; Glycine max - genetics; Glycine max - physiology; growth and development; Helix-loop-helix proteins (basic); leaf development; Leaves; Lipoxygenase; Lipoxygenase - genetics; Lipoxygenase - metabolism; Metabolic pathways; Metabolism; nitrogen; Nucleotide Motifs - genetics; phenotype; Physiology; Plant Infertility - genetics; Plant Leaves - genetics; Plant Leaves - physiology; Plant Proteins - genetics; Plant Proteins - metabolism; Plants; Promoter Regions, Genetic - genetics; Proteins; Regulatory Sequences, Nucleic Acid - genetics; Resource partitioning; Senescence; Soybeans; Starch; stay‐green; sterile; Storage proteins; tissues; transcription (genetics); Transcription factors; Transcription Factors - metabolism; Yellowing; stay-green; lipoxygenase; depodded; expression profiling; sterile
• ISSN: 0140-7791; 1365-3040; 1365-3040
• DOI: 10.1111/pce.13030

The absence of a reproductive sink causes physiological and morphological changes in soybean plants. These include increased accumulation of nitrogen and starch in the leaves and delayed leaf senescence. To identify transcriptional changes that occur in leaves of these sink‐limited plants, we used RNAseq to compare gene expression levels in trifoliate leaves from depodded and ms6 male‐sterile soybean plants and control plants. In both sink‐limited tissues, we observed a deferral of the expression of senescence‐associated genes and a continued expression of genes associated with leaf maturity. Gene Ontology‐terms (GO‐terms) associated with growth and development and storage proteins were over‐represented in genes that were differentially expressed in sink‐limited tissues. We also identified basic helix‐loop‐helix, auxin response factor, and squamosa binding protein transcription factors expressed in sink‐limited tissues, and the senescing control leaves expressed WRKY and NAC transcription factors. We identified genes that were not expressed during normal leaf development but that were highly expressed in sink‐limited plants, including the SGR3b “non‐yellowing” gene. These differences highlighted several metabolic pathways that were involved in distinct modes of resource partitioning of leaves with the “stay green” phenotype. This paper describes the transcriptional differences in soybean leaves where the normal pattern of senescence is delayed by either the removal of or absence of pods. Although the phenomenon of senescence delay is common among plants, and has been physiologically characterized for the obvious potential to impact seed filling and yield, it has not yet been subject to a molecular analysis using modern transcriptional profiling technologies. Applying these techniques in controlled conditions, we found evidence for expression of a new member of the non‐yellowing gene family in soybean that is related to Mendel's green cotyledon gene from pea. We also observed upregulation of genes from the lipoxygenase gene family and the squamosa binding protein transcription factor family. We think that these results provide some insight into the metabolic and physiological changes that occur in sink‐limited leaves and open avenues for future research into the regulation of senescence in soybean.