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Title: Transcriptome analysis of soybean leaf abscission identifies transcriptional regulators of organ polarity and cell fate

item KIM, JOONYUP - University Of Maryland
item Barnaby, Jinyoung
item Yang, Ronghui
item Sicher Jr, Richard
item CHANG, CAREN - University Of Maryland
item Tucker, Mark

Submitted to: Frontiers in Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/22/2016
Publication Date: 2/17/2016
Citation: Kim, J., Barnaby, J.Y., Yang, R., Sicher Jr, R.C., Chang, C., Tucker, M.L. 2016. Transcriptome analysis of soybean leaf abscission identifies transcriptional regulators of organ polarity and cell fate. Frontiers in Plant Science. 7:125.

Interpretive Summary: Abscission, organ separation, is a cell separation event that occurs in a finite layer of cells at the base of an organ, e.g. leaf, flower, fruit, petals, etc. We are interested in identifying proteins (transcription factors) and mechanisms that regulate the expression of soybean genes that are involved in the cell separation event, cell wall degradation. We have identified 120 transcription factors that change significantly in the cells that undergo extensive cell wall degradation. These regulatory proteins and their corresponding genes are targets that can be manipulated to control premature organ separation and embryo abortion. Controlling these factors during periods of environmental stress can increase crop yield.

Technical Abstract: Abscission, organ detachment, is a developmental process that is modulated by environmental factors. To understand the molecular events underlying the progression of abscission in soybean, we induced abscission in 21 day-old soybean by treating leaf explants with ethylene. RNA-seq was completed for RNA isolated from the leaf abscission zones (LAZ) and petioles (Non-AZ, NAZ) after 0, 12, 24, 48, and 72h of ethylene treatment. Cluster analysis was performed for genes that were significantly expressed in the LAZ compared with the NAZ (p<1%) and significantly up or down-regulated over time. As expected, expression of various families of cell wall modifying enzymes and small proteins/polypeptides (e.g., IDA and PAR1) specifically followed the progression of abscission as did, many PR related genes such as pathogen-related PR1, CAP and Thaumtin. Here, we focus on the 5,206 soybean genes we identified as having transcription activity, primarily transcription factors (TFs). Of the 5,206 TFs, 1,387 were 8-fold up or down-regulated in the LAZ, but only 120 of these were 8-fold LAZ-specific compared to NAZ. Of these 120 TFs, 40 were 8-fold up-regulated and 80 down-regulated. The 120 LAZ-specific TFs in this grouping included MYB, bHLH, WRKY, zinc finger proteins, GRAS, NAC, and homeodomain TFs. More detailed analyses and comparisons are described and discussed and also compared with earlier studies of TF binding to the proximal promoter of the bean abscission cellulase (BAC1).