Submitted to: Plant Physiology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/25/2013
Publication Date: 10/8/2012
Citation: Tucker, M.L., Yang, R. 2012. Expression analysis in soybean of IDA-like, HAESA-like and other key regulatory proteins during leaf abscission and cyst nematode infected roots. Plant Physiology. doi:10.1093/aobpla/pls035. Interpretive Summary: Soybean cyst nematode (SCN) is the most economically damaging pathogen of soybean. It has been estimated that SCN damage to the United States soybean crop costs farmers one billion dollars annually. SCN induces the formation of its feeding structure by breaking down the walls between root cells to form a much larger cell. We previously demonstrated that the SCN induced breakdown of cell walls is accomplished in a manner similar to the cell wall breakdown that occurs during separation of leaves and flowers from the parent plant. A protein named IDA is an important inductive signal for cell wall breakdown in other plants. We examined the role of IDA in soybean leaf drop and SCN infection of roots. IDA was clearly an important signal for soybean leaf drop. However, the role of IDA in SCN infection was less certain but still of interest for further study. A better understanding of how SCN induces the formation of a functional feeding structure in roots will greatly improve the ability of scientists and industrial partners to control SCN infection of soybean.
Technical Abstract: The stimulatory and inhibitory role of ethylene and auxin, respectively, in leaf abscission is well documented. More recently, IDA peptides and their putative interacting receptor like kinase partner, HAESA, were shown to be essential components in Arabidopsis floral organ abscission. It was proposed that the IDA signaling path might also regulate other cell separation events in plants. We identified 12 IDA-like and 11 HAESA-like proteins in soybean (Glycine max) and monitored their gene expression in conjunction with multiple cell wall modifying proteins, 17 ACC synthases and 2 auxin conjugating proteins (GH3) during leaf abscission and infection of roots with soybean cyst nematodes (SCN; Heterodera glycines). Several members of each of these gene families are up-regulated during abscission and ethylene evoked the early expression of nearly all of them. Interestingly, some IDA and HAESA-like genes were up-regulated independent of ethylene. Formation of the feeding structure (syncytium) for SCN requires the degradation of cell walls between adjoining cells and it was hypothesized that IDA signaling might be involved in this process. Genes for several cell wall modifying proteins and ACS were up-regulated during SCN colonization of root pieces and both GH3 genes and two HAESA genes were slightly up-regulated in SCN colonized roots. However, no significant changes in the expression of IDA were observed at the SCN infection site. It was hypothesized that the nematode might secrete an IDA-like effector. A search of nematode sequence data revealed IDA-like open reading frames in three root-knot nematodes (genus Meloidogyne), but none in cyst nematodes.