Functional analysis of an Arabidopsis transcription factor WRKY25 in heat stress

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127

Arabidopsis thaliana WRKY39, a transcription factor that is induced by heat stress, is a member of the group II WRKY proteins and responds to both abiotic and biotic stress. Heat-treated seeds and plants of WRKY39 knock-down mutants had increased susceptibility to heat stress, showing reduced germination, decreased survival, and elevated electrolyte leakage compared with wild-type plants. In contrast, WRKY39 over-expressing plants exhibited enhanced thermotolerance compared with wild-type plants. RT-PCR and qRT-PCR analysis of wrky39 mutants and WRKY39 over-expressing plants identified putative genes regulated by WRKY39. Consistent with a role for WRKY39 in heat tolerance, the expression levels of salicylic acid (SA)-regulated PR1 and SA-related MBF1c genes were downregulated in wrky39 mutants. In contrast, over-expression of WRKY39 increased the expression of PR1 and MBF1c. The WRKY39 transcript was induced in response to treatment with SA or methyljasmonate. Analysis of heat stressinduced WRKY39 in defense signaling mutants, including coi1, ein2, and sid2, further indicated that WRKY39 was positively co-regulated by the SA and jasmonate (JA) signaling pathways. Together, these findings reveal that heat stress-induced WRKY39 positively regulates the cooperation between the SA-and JA-activated signaling pathways that mediate responses to heat stress.

Section: Plant Materials and Growth Conditionsmentioning

confidence: 99%

Functional Characterization of Arabidopsis thaliana WRKY39 in Heat Stress

Zhou

Chen

et al. 2010

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210

127

“…WRKY proteins are a superfamily of transcription factors with potential regulatory roles related to various biotic and abiotic stress responses. Arabidopsis WRKY proteins participate in regulation of plant development (Johnson et al, 2002), material metabolism (Devaiah et al, 2007), abiotic stress (Li et al, 2009;2010;Qiu et al, 2009), seed dormancy and germination (Jiang et al, 2009). They also regulate plant responses to disease resistance and establish the corresponding pathway of signal transduction (Chen et al, 2002;Journot-Catalino et al, 2006;Yu et al, 2001).…”

Section: Introductionmentioning

confidence: 99%

WRKY22 Transcription Factor Mediates Dark-Induced Leaf Senescence in Arabidopsis

Zhou

Jiang

2011

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268

181

Arabidopsis WRKY proteins are plant-specific transcription factors, encoded by a large gene family, which contain the highly conserved amino acid sequence WRKYGQK and the zinc-finger-like motifs, Cys 2 His 2 or Cys 2 HisCys. They can recognize and bind the TTGAC(C/T) W-box ciselements found in the promoters of target genes, and are involved in the regulation of gene expression during pathogen defense, wounding, trichome development, and senescence. Here we investigated the physiological function of the Arabidopsis WRKY22 transcription factor during dark-induced senescence. WRKY22 transcription was suppressed by light and promoted by darkness. In addition, AtWRKY22 expression was markedly induced by H 2 O 2 . These results indicated that AtWRKY22 was involved in signal pathways in response to abiotic stress. Darktreated AtWRKY22 over-expression and knockout lines showed accelerated and delayed senescence phenotypes, respectively, and senescence-associated genes exhibited increased and decreased expression levels. Mutual regulation existed between AtWRKY22 and AtWRKY6, AtWR-KY53, and AtWRKY70, respectively. Moreover, AtWRKY22 could influence their relative expression levels by feedback regulation or by other, as yet unknown mechanisms in response to dark. These results prove that AtWRKY22 participates in the dark-induced senescence signal transduction pathway.

“…4E). Hypocotyl elongation, survival rate of seedling, and electrolyte leakage assay are effective parameters in analysis of heat tolerance (Clark et al, 2004;Hong and Vierling, 2000;Li et al, 2009). The AtNRP1-overexpressing transgenic plants showed decreased thermotolerance at different growth stages and the null mutation at the AtNRP1 gene was the same as WT under heat stress, which indicated that the single-gene mutation of AtNRP1 was insufficient to alter heat tolerance.…”

Section: Discussionmentioning

confidence: 99%

Identification of an Arabidopsis Nodulin-Related Protein in Heat Stress

2010

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We identified a Nodulin-related protein 1 (NRP1) encoded by At2g03440, which was previously reported to be RPS2 interacting protein in yeast-two-hybrid assay. Northern blotting showed that AtNRP1 expression was suppressed by heat stress (42°C) and induced by low temperature (4°C) treatment. Strong GUS staining was observed in the sites of meristematic tissues of pAtNRP1:: GUS transgenic plants, such as shoot apex and root tips, young leaf veins, stamens and stigmas of flowers, and abscission layers of young siliques. To study AtNRP1 biological functions, we have characterized both loss-of-function T-DNA insertion and transgenic overexpression plants for AtNRP1 in Arabidopsis. The T-DNA insertion mutants displayed no obvious difference as compared to wild-type Arabidopsis under heat stress, but the significant enhanced susceptibility to heat stress was revealed in two independent AtNRP1-overexpressing transgenic lines. Further study found that the decreased thermtolerance in AtNRP1-overexpressing lines accompanied significantly decreased accumulation of ABA after heat treatment, which was probably due to AtNRP1 playing a role in negative-feedback regulation of the ABA synthesis pathway. These results support the viewpoint that the application of ABA inhibits nodulation and nodulin-related gene expression and threaten adverse ambient temperature can impact the nodulin-related gene expression.