Abstract
AtMYB44 belongs to the R2R3 MYB subgroup 22 transcription factor family in Arabidopsis (Arabidopsis thaliana). Treatment with abscisic acid (ABA) induced AtMYB44 transcript accumulation within 30 min. The gene was also activated under various abiotic stresses, such as dehydration, low temperature, and salinity. In transgenic Arabidopsis carrying an AtMYB44 promoter-driven beta-glucuronidase (GUS) construct, strong GUS activity was observed in the vasculature and leaf epidermal guard cells. Transgenic Arabidopsis overexpressing AtMYB44 is more sensitive to ABA and has a more rapid ABA-induced stomatal closure response than wild-type and atmyb44 knockout plants. Transgenic plants exhibited a reduced rate of water loss, as measured by the fresh-weight loss of detached shoots, and remarkably enhanced tolerance to drought and salt stress compared to wild-type plants. Microarray analysis and northern blots revealed that salt-induced activation of the genes that encode a group of serine/threonine protein phosphatases 2C (PP2Cs), such as ABI1, ABI2, AtPP2CA, HAB1, and HAB2, was diminished in transgenic plants overexpressing AtMYB44. By contrast, the atmyb44 knockout mutant line exhibited enhanced salt-induced expression of PP2C-encoding genes and reduced drought/salt stress tolerance compared to wild-type plants. Therefore, enhanced abiotic stress tolerance of transgenic Arabidopsis overexpressing AtMYB44 was conferred by reduced expression of genes encoding PP2Cs, which have been described as negative regulators of ABA signaling.
Highlights
AtMYB44 belongs to the R2R3 MYB subgroup 22 transcription factor family in Arabidopsis (Arabidopsis thaliana)
Northern blots showed that AtMYB44 transcript accumulation was induced within 30 min after the application of 100 mM abscisic acid (ABA), 100 mM methyl jasmonate, or 50 mM ethylene to Arabidopsis rosette leaves (Fig. 1A)
Arabidopsis AtMYB44 Transcription Factor script levels occurred before the increase in RD29A transcripts, which was detected at least 1 h after hormone or stress treatment
Summary
AtMYB44 belongs to the R2R3 MYB subgroup 22 transcription factor family in Arabidopsis (Arabidopsis thaliana). The atmyb knockout mutant line exhibited enhanced salt-induced expression of PP2C-encoding genes and reduced drought/salt stress tolerance compared to wild-type plants. Enhanced abiotic stress tolerance of transgenic Arabidopsis overexpressing AtMYB44 was conferred by reduced expression of genes encoding PP2Cs, which have been described as negative regulators of ABA signaling. Over 1,600 transcription factors, representing approximately 6% of the total number of genes, have been identified in the Arabidopsis (Arabidopsis thaliana) genome (Arabidopsis Genome Initiative, 2000; Riechmann et al, 2000; Gong et al, 2004). These transcription factors can be classified into several families based on the structure of their DNA-binding domains. The roles of individual plant R2R3 MYB proteins in diverse plant processes have been explored, including hormonal signaling, cell cycle control, stress responses, secondary metabolism, cellular morphogenesis, and meristem formation (Martin and Paz-Ares, 1997; Jin and Martin, 1999)
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