Overexpression of AtMYB44 Enhances Stomatal Closure to Confer Abiotic Stress Tolerance in Transgenic Arabidopsis

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 promoterdriven b-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.

MYB transcription factor genes as regulators for plant responses: an overview

“…Akagi et al (2010) characterized DkMYB2, a Myb-like transcription factors (MYB-TF), which was placed in a subclade including a PA regulator of Arabidopsis (Arabidopsis thaliana), TRANSPARENT TESTA2 (TT2), and was co-induced with PA pathway genes after wound stress. AtMYB44/AtMYBR1 regulated ABA-mediated stomatal closure in response to abiotic stresses and three other members of this subgroup (AtMYB70, AtMYB73 and AtMYB77/AtMYBR2) are likely to be associated with stress responses (Jung et al 2008). AtMYB13, AtMYB15, AtMYB33 and AtMYB101 (Reyes and Chua 2007) were involved in ABA-mediated responses to environmental signals.…”

The Grapevine Expression Atlas Reveals a Deep Transcriptome Shift Driving the Entire Plant into a Maturation Program

“…Topic 4 was represented by a small number of genes, mainly encoding stress and hormone response proteins, such as metallothionein and dehydrin, an ABA-INDUCED WHEAT PLASMA MEMBRANE-19 protein homolog that could mediate ABA-induced freezing tolerance, and the dormancy regulator DRM1. Topic 4 also contained an AtMYB73 homolog, which is related to cold acclimation in Arabidopsis (Jung et al, 2008).…”

Quadruple 9-mer-Based Protein Binding Microarray Analysis Confirms AACnG as the Consensus Nucleotide Sequence Sufficient for the Specific Binding of AtMYB44

“…AtMYB44 regulates diverse cellular responses mediated by abscisic acid (Jung et al, 2008), jasmonate (Jung et al, 2010) and ethylene (Liu et al, 2010;Lü et al, 2011). Our data suggest that functional diversity of AtMYB44 among the type I MYB transcription factors is not due to their binding specificity on a particular promoter sequence.…”

“…For transgenic Arabidopsis, microarray analysis showed that in the absence of salt treatment, the overall gene expression patterns were not significantly different from those of wild-type plants (Jung et al, 2008). Thus, AtMYB44 overproduction in itself does not appear to be sufficient to regulate the expression of a group of specific target genes.…”

“…We reported previously that the AtMYB44 transcription factor plays a role in the abscisic acid (ABA)-mediated signaling pathway that confers abiotic stress tolerance via the enhancement of stomatal closure in Arabidopsis thaliana (Jung et al, 2008). Transgenic Arabidopsis overexpressing the gene exhibited enhanced drought/salinity tolerance by suppressing the expression of genes encoding a group of Ser/Thr protein phosphatase 2Cs (PP2Cs) that were described as negative regulators of ABA signaling.…”