A novel Sec14 phospholipid transfer protein from Nicotiana benthamiana is up-regulated in response to Ralstonia solanacearum infection, pathogen associated molecular patterns and effector molecules and involved in plant immunity
To elucidate the molecular mechanisms of plant immune responses, we isolated genes whose expression was regulated by inoculation with Ralstonia solanacearum. Here, we report the characterization of Nicotiana benthamiana belonging to the SEC14-gene superfamily designated as Nicotiana benthamiana SEC14 (NbSEC14). NbSEC14 rescued growth defects and impaired invertase secretion associated with the yeast sec14p temperature-sensitive mutant, while recombinant NbSec14 protein had phospholipids transfer activity. NbSEC14 expression was up-regulated in N. benthamiana leaves after inoculation with virulent or avirulent R. solanacearum. Expression of NbSEC14 was induced by treatment with chitin, flg22, and by Agrobacterium-mediated transient expression of INF1 elicitin, AvrA from R. solanacearum, and co-expression of the capsid protein from Tobacco mild green mosaic virus with its cognate resistance L1 protein. NbSEC14-silenced plants showed accelerated growth of both the virulent and avirulent R. solanacearum as well as acceleration of disease development. This study may provide useful information for the further analysis of the function of plant Sec14 protein homologs in the regulation of plant immune responses.
"NbSEC14 rescued temperature-sensitive growth mutant of sec14 in yeast, and NbSEC14 protein showed phospholipid transfer activity. Moreover, acceleration of disease development of bacterial wilt and growth of R. solanacearum were observed in the NbSEC14-silenced plants . SEC14 protein belongs to the large yet under-characterized Sec14-protein superfamily (1550 proteins) originally isolated from Saccharomyces cerevisiae
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[Show abstract][Hide abstract] ABSTRACT: We previously identified a gene related to the SEC14-gene phospholipid transfer protein superfamily that is induced in Nicotiana benthamiana (NbSEC14) in response to infection with Ralstonia solanacearum. We here report that NbSEC14 plays a role in plant immune responses via phospholipid-turnover. NbSEC14-silencing compromised expression of defense-related PR-4 and accumulation of jasmonic acid (JA) and its derivative JA-Ile. Transient expression of NbSEC14 induced PR-4 gene expression. Activities of diacylglycerol kinase, phospholipase C and D, and the synthesis of diacylglycerol and phosphatidic acid elicited by avirulent R. solanacearum were reduced in NbSEC14-silenced plants. Accumulation of signaling lipids and activation of diacylglycerol kinase and phospholipases were enhanced by transient expression of NbSEC14. These results suggest that the NbSEC14 protein plays a role at the interface between lipid signaling-metabolism and plant innate immune responses.
PLoS ONE 05/2014; 9(5):e98150. DOI:10.1371/journal.pone.0098150 · 3.23 Impact Factor
"Recently, it was reported that PA directly binds to Ca2+-dependent protein kinases, promoting the activities of these enzymes to activate intracellular signaling . Previously, we reported that the NbSEC14 lipid transfer protein affected phospholipase activity and PA content, leading to plant immune responses in response to pathogen infection . The results of the present study suggests that the DS1 phenotype was due to activation of rboHB-dependent ROS production and Coi1-regulated JA-dependent immune responses, since enhanced resistance decreased in the double-knock down of DS1 and NbrbohB or NbCoil (Figures 6, 7). "
[Show abstract][Hide abstract] ABSTRACT: Nicotianabenthamiana is susceptible to Ralstonia solanacearum. To analyze molecular mechanisms for disease susceptibility, we screened a gene-silenced plant showing resistance to R. solanacearum, designated as DS1 (Disease suppression 1). The deduced amino acid sequence of DS1 cDNA encoded a phosphatidic acid phosphatase (PAP) 2. DS1 expression was induced by infection with a virulent strain of R. solanacearum in an hrp-gene-dependent manner. DS1 rescued growth defects of the temperature-sensitive ∆lpp1∆dpp1∆pah1 mutant yeast. Recombinant DS1 protein showed Mg(2+)-independent PAP activity. DS1 plants showed reduced PAP activity and increased phosphatidic acid (PA) content. After inoculation with R. solanacearum, DS1 plants showed accelerated cell death, over-accumulation of reactive oxygen species (ROS), and hyper-induction of PR-4 expression. In contrast, DS1-overexpressing tobacco plants showed reduced PA content, greater susceptibility to R. solanacearum, and reduced ROS production and PR-4 expression. The DS1 phenotype was partially compromised in the plants in which both DS1 and NbCoi1 or DS1 and NbrbohB were silenced. These results show that DS1 PAP may affect plant immune responses related to ROS and JA cascades via regulation of PA levels. Suppression of DS1 function or DS1 expression could rapidly activate plant defenses to achieve effective resistance against Ralstonia solanacearum.
PLoS ONE 09/2013; 8(9):e75124. DOI:10.1371/journal.pone.0075124 · 3.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We have been isolating and characterizing Ralstonia solanacearum-responsive genes (RsRGs) in Nicotiana plants. In this study we focused on RsRG308, which we renamed NbTCTP (N. benthamiana translationally controlled tumor protein) because it encodes a polypeptide showing similarity to translationally controlled tumor proteins. Induction of HR was accelerated in NbTCTP-silenced N. benthamiana plants challenged with R. solanacearum 8107 (Rs8107). The Rs8107 population decreased significantly, whereas hin1 gene expression was enhanced in the silenced plant. Accelerated induction of HR was observed in NbTCTP-silenced plants inoculated with Pseudomonas cichorii and P. syringae pv. syringae. Silencing of NbTCTP also accelerated the induction of HR cell death by Agrobacterium-mediated transient expression of HR inducers, such as AvrA, BAX, INF1 and NbMEK2(DD). NbTCTP silencing enhanced NbrbohB- and NbMEK2-mediated ROS production leading to HR. Ttransient expression of both the full-length sequence and the Bcl-xL domain of NbTCTP decreased HR cell death induced by Agrobacterium-mediated transient expression of HR inducers. NbTCTP-silenced plants also showed slightly dwarf phenotypes. Therefore, NbTCTP might have a role in cell death regulation during HR to fine tune PCD-associated plant defense responses.
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