|ZHAO, NAN - University Of Tennessee|
|LAN, SUQUE - Hebei Academy Of Agriculture|
|JIA, QIDONG - University Of Tennessee|
|GUO, HONG - University Of Tennessee|
|CHEN, FENG - University Of Tennessee|
Submitted to: Plant Physiology and Biochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/16/2016
Publication Date: 2/18/2016
Citation: Zhao, N., Lin, H., Lan, S., Jia, Q., Guo, H., Chen, F. 2016. VvMJE1 of the grapevine (Vitis vinifera) VvMES methylesterase family encodes for methyl jasmonate esterase and has a role in stress response. Plant Physiology and Biochemistry. 102:125-132.
Interpretive Summary: Grape methyl esterase (MES) catalyzes metabolism of jasmonic acid, a phytohormone involved with the regulation of plant development and defense responses to environmental stresses. In this study, gene sequences of MES were identified through homologous sequence analysis in the grapevine genome. The putative gene function was further characterized through molecular and biochemical approaches. In-planta experiments confirmed that MES had a regulatory role in response to abiotic stresses such as cold. This study provides new information that advances knowledge in understanding stress physiology of grapevine.
Technical Abstract: The known members of the plant methyl esterase (MES) family catalyze hydrolysis of a C-O ester linkage of methyl esters of several phytohormones including indole-3-acetic acid, salicylic acid, and jasmonic acid. The genome of grapevine (Vitis vinifera) was found to contain 15 MES genes, designated VvMES1-15. In this report, VvMES5 was selected for molecular, biochemical, and structural studies. VvMES5 is most similar to tomato methyl jasmonate esterase (LeMJE). E. coli-expressed recombinant VvMES5 displayed methyl jasmonate (MeJA) esterase activity, and it was renamed VvMJE1. Under steady-state conditions, VvMJE1 exhibited an apparent Km value of 92.9 µM with MeJA. VvMJE1 was also shown to have lower activity with methyl salicylate (MeSA), another known substrate of the MES family, and only at high concentrations of substrate. To understand the structural basis of VvMJE1 in discriminating MeJA and MeSA, a homolog model of VvMJE1 was made using the X-ray structure of tobacco SABP2, which encodes for methyl salicylate esterase, as a template. In VvMJE1, the catalytic triad (Ser82, His239 and Asp211) is highly conserved with those of tobacco SABP2, and the three residues in the homology model are in good alignment with the corresponding residues in the X-ray structure of SABP2. Interestingly, two bulky residues at the binding site and near the surface of tobacco SABP2 are replaced by relatively small residues in VvMJE1. Such a change enables the accommodation of a larger substrate MeJA in VvMJE1. The expression of VvMJE1 was significantly up-regulated by two stress factors, suggesting that VvMJE1 has a role in response of grape plants to stresses.