Gene coding for SigA-binding protein from Arabidopsis appears to be transcriptionally up-regulated by salicylic acid and NPR1-dependent mechanisms

Abstract

SigA-binding protein (SIB A) is a nuclearencoded chloroplast-targeted protein that interacts with the plastid-encoded plastid RNA polymerase r-factor SigA (Sig1). In this study, the SIB A gene responded rapidly to salicylic acid (SA) treatment, but responded slowly to ethylene (ET) and jasmonic acid (JA) treatments as determined with microarray and quantitative real-time RT-PCR analyses. Expression of the SIB A gene increased rapidly, with a peak at 2 h after SA treatment and then decreased gradually. In contrast, expression of the PR-1 gene, a marker gene on the SA defense signaling pathway, increased gradually between 0 and 24 h after SA treatment. In addition, transcription levels of SIB A and PR-1 decreased between 0 and 24 h in the benzothiadiazole (BTH)-treated npr1-1 plants. We suggest that the SIB A gene is downstream of NPR1 on the SA signaling pathway. From the results of our analysis of the 1.5-kbp promoter region of the SIB A gene in Arabidopsis, the isolated promoter region of the SIB A gene seems able to drive the transcription of the GUS gene to elevated levels more rapidly in transgenic Arabidopsis plants undergoing SA treatment compared with levels of PR-1. To analyze biological function of SIB A and investigate SIB A-regulated genes, we generated transgenic Arabidopsis plants in which SIB A was overexpressed. As a result, ROS-related genes, such as glutathione transferase, were up-regulated in plants overexpressing SIB A. However, SIB A-overexpressing plants were not resistant to Pseudomonas syringae pv. tomato DC3000 strain. The SIB A gene has promise as a new tool to analyze the SA-signaling pathway and the role of the chloroplast in plant defense responses.

The VQ Motif-Containing Protein Family of Plant-Specific Transcriptional Regulators

“…Thus, VQ23 positively regulates the plant defense response against both necrotrophic and biotrophic pathogens likely via a WRKY-dependent signaling pathway. However, it was reported that VQ23 overexpression plants do not differ from the control with respect to their sensitivity to the virulent strain P. syringae pv tobacco (Pst) DC3000 (Narusaka et al, 2008). VQ16/SIB2 plays a redundant role in response to B. cinerea infection with VQ23 (Lai et al, 2011), consistent with their evolutionary relatedness in VQ group VI.…”

“…The transcription of VQ genes is modulated by multiple endogenous and environmental signals, consistent with their diverse roles in stress responses and during plant growth and development. For instance, B. cinerea infection and SA treatment rapidly and strongly induce VQ23 and VQ16 transcript levels (Narusaka et al, 2008;Xie et al, 2010;Lai et al, 2011). VQ22 transcript is significantly increased upon JA treatment and quickly accumulates after mechanical wounding (Hu et al, 2013a).…”

Arabidopsis VQ MOTIF-CONTAINING PROTEIN29 Represses Seedling Deetiolation by Interacting with PHYTOCHROME-INTERACTING FACTOR1

“…Accumulating studies suggest that members of the VQ family play diverse functions, such as regulating the plant defense response (Andreasson et al, 2005;Narusaka et al, 2008;Xie et al, 2010;Lai et al, 2011), abiotic stress resistance (Perruc et al, 2004;Hu et al, 2013), and seed development (Wang et al, 2010). Our study provides genetic and molecular evidence that VQ29 has a prominent role in plant growth and development in response to the light environment, thus extending the functionality of this plant-specific protein family.…”

“…The functions of a few members of this family has been characterized to date. For example, SIGMA FACTOR BINDING PROTEIN1 (SIB1/VQ23), its close homolog SIB2 (VQ16), and MITOGEN-ACTIVATED PROTEIN KINASE4 SUB-STRATE1 (VQ21) are required for the plant defense response (Andreasson et al, 2005;Narusaka et al, 2008;Xie et al, 2010;Lai et al, 2011). In addition, HAIKU1 (VQ14) is a regulator of endosperm growth and seed size (Wang et al, 2010), while CALMODULIN-BINDING PRO-TEIN25 (VQ15) and VQ9 function as negative effectors of osmotic and salinity stress tolerance, respectively (Perruc et al, 2004;Hu et al, 2013).…”

ArabidopsisSigma Factor Binding Proteins Are Activators of the WRKY33 Transcription Factor in Plant Defense

“…In B. cinereainfected plants, the transcript levels of SIB1 and SIB2 were markedly enhanced, similar to those of WRKY33 (Figure 7). SIB1 is also induced by SA and the bacterial pathogen P. syringae (Narusaka et al, 2008;Xie et al, 2010). Pathogen-induced Figure 6.…”