AUTHOR=Sheshukova Ekaterina V. , Komarova Tatiana V. , Pozdyshev Denis V. , Ershova Natalia M. , Shindyapina Anastasia V. , Tashlitsky Vadim N. , Sheval Eugene V. , Dorokhov Yuri L. 

TITLE=The Intergenic Interplay between Aldose 1-Epimerase-Like Protein and Pectin Methylesterase in Abiotic and Biotic Stress Control

JOURNAL=Frontiers in Plant Science

VOLUME=8

YEAR=2017

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2017.01646

DOI=10.3389/fpls.2017.01646

ISSN=1664-462X

ABSTRACT=<p>The mechanical damage that often precedes the penetration of a leaf by a pathogen promotes the activation of pectin methylesterase (PME); the activation of PME leads to the emission of methanol, resulting in a “priming” effect on intact leaves, which is accompanied by an increased sensitivity to <italic>Tobacco mosaic virus</italic> (TMV) and resistance to bacteria. In this study, we revealed that mRNA levels of the methanol-inducible gene encoding <italic>Nicotiana benthamiana</italic> aldose 1-epimerase-like protein (NbAELP) in the leaves of intact plants are very low compared with roots. However, stress and pathogen attack increased the accumulation of the <italic>NbAELP</italic> mRNA in the leaves. Using transiently transformed plants, we obtained data to support the mechanism underlying AELP/PME-related negative feedback The insertion of the <italic>NbAELP</italic> promoter sequence (proNbAELP) into the <italic>N. benthamiana</italic> genome resulted in the co-suppression of the natural <italic>NbAELP</italic> gene expression, accompanied by a reduction in the <italic>NbAELP</italic> mRNA content and increased PME synthesis. Knockdown of <italic>NbAELP</italic> resulted in high activity of PME in the cell wall and a decrease in the leaf glucose level, creating unfavorable conditions for <italic>Agrobacterium tumefaciens</italic> reproduction in injected leaves. Our results showed that NbAELP is capable of binding the TMV movement protein (MP<sub>TMV</sub>) <italic>in vitro</italic> and is likely to affect the cellular nucleocytoplasmic transport, which may explain the sensitivity of <italic>NbAELP</italic> knockdown plants to TMV. Although NbAELP was primarily detected in the cell wall, the influence of this protein on cellular <italic>PME</italic> mRNA levels might be associated with reduced transcriptional activity of the <italic>PME</italic> gene in the nucleus. To confirm this hypothesis, we isolated the <italic>N. tabacum PME</italic> gene promoter (proNtPME) and showed the inhibition of proNtPME-directed <italic>GFP</italic> and <italic>GUS</italic> expression in leaves when co-agroinjected with the NbAELP-encoding plasmid. We hypothesized that plant wounding and/or pathogen attack lead to PME activation and increased methanol emission, followed by increased <italic>NbAELP</italic> expression, which results in reversion of <italic>PME</italic> mRNA level and methanol emission to levels found in the intact plant.</p>