Overexpression of TMAC2, a novel negative regulator of abscisic acid and salinity responses, has pleiotropic effects in Arabidopsis thaliana

Abstract

Phytohormone abscisic acid (ABA) regulates many aspects of plant development and growth. To explore the molecular mechanism of ABA, we identified the novel ABA-regulated genes in Arabidopsis thaliana by searching for genes possessing two or more ABREs (ABA-responsive elements). One of these genes, two or more ABREs-containing gene 2 (TMAC2) is highly induced by ABA and NaC1. Database searches revealed that TMAC2 encodes a protein with no domains of known function. Expression of TMAC2-GFP fusion protein in Arabidopsis mesophyll protoplasts indicated that TMAC2 is targeted to the nucleus. Although the gene has a basal level of expression in various Arabidopsis organs/tissues except for adult leaves, a high expression level was detected in roots. Constitutive overexpression of TMAC2 in plants resulted in the insensitivity to ABA and NaCl, suggesting that TMAC2 plays a negative role in ABA and salt stress responses. Furthermore, TMAC2-overexpressing plants exhibited the short roots, late flowering and starch-excess phenotypes. RT-PCR analysis showed that decreased expression of two floral- and one starch degradation-related genes, SOC1/AGL20 and SEP3/AGL9, and SEX1, respectively, may lead to altered phenotypes of TMAC2-overexpressing plants. Taken together, our data reveal that TMAC2 acts in the nucleus and is an important negative regulator of ABA and salt stress responses, and could play a critical role in controlling root elongation, floral initiation and starch degradation.

Genome-wide identification of Thellungiella salsuginea microRNAs with putative roles in the salt stress response

“…These miRNAs may function as key regulators of the salt stress response in T. salsuginea. Previous functional studies of the predicted target genes of tsa-miRn7 and PC069 support this hypothesis [29,30] (Additional file 7: Table S8). Considering the environmental, developmental, and tissue-specific regulation of miRNA expression, the miRNAs identified in our study probably represent only part of the T. salsuginea miRNA population.…”

POWERDRESS interacts with HISTONE DEACETYLASE 9 to promote aging in Arabidopsis

“…Given the function of HDA9 in leaf senescence, we sought to investigate whether HDA9 directly regulate genes involved in this process. By searching the 222 genes with HDA9 binding and upregulation in hda9, we found 11 genes with potential or known functions in senescence (Figure 5—figure supplement 1G), including catalase that protects cells from oxidative damage (CAT1) (Du et al, 2008), autophagy proteins that delay senescence and programmed cell death (APG9, ATG2, ATG8E and ATG13) (Hanaoka et al, 2002; Yoshimoto et al, 2004; Suttangkakul et al, 2011; Wang et al, 2011b), proteins that negatively regulate ABA signaling pathway known to promote senescence (NPX1, PLL5, AFP2, AFP4) (Schweighofer et al, 2004; Huang and Wu, 2007; Garcia et al, 2008; Kim et al, 2009b), BIK1 that negatively regulates the salicylic acid (SA) signaling pathway (Veronese et al, 2006), and WRKY57 (a WRKY family transcription factor) acts as a negative regulator of JA to prevent leaf senescence (Jiang et al, 2014). …”

Arabidopsis Defense against Botrytis cinerea: Chronology and Regulation Deciphered by High-Resolution Temporal Transcriptomic Analysis

“…Two hours later (22 HAI) upregulation of negative regulators of ABA signaling begins. ABI1 and ABI2, two protein phosphatases involved in the core ABA pathway, are induced along with two repressors of ABA responses: ABR1, thought to be a transcriptional repressor (Pandey et al, 2005), and TMAC2, a nuclear-localized protein (Huang and Wu, 2007). AZF2 also has a TOFDE of 22 HAI and is another repressor of ABA signaling (Drechsel et al, 2010).…”