Arabidopsis type B cytokinin response regulators ARR1, ARR10, and ARR12 negatively regulate plant responses to drought

Abstract

In this study, we used a loss-of-function approach to elucidate the functions of three Arabidopsis type B response regulators (ARRs)-namely ARR1, ARR10, and ARR12-in regulating the Arabidopsis plant responses to drought. The arr1,10,12 triple mutant showed a significant increase in drought tolerance versus WT plants, as indicated by its higher relative water content and survival rate on drying soil. This enhanced drought tolerance of arr1,10,12 plants can be attributed to enhanced cell membrane integrity, increased anthocyanin biosynthesis, abscisic acid (ABA) hypersensitivity, and reduced stomatal aperture, but not to altered stomatal density. Further drought-tolerance tests of lower-order double and single mutants indicated that ARR1, ARR10, and ARR12 negatively and redundantly control plant responses to drought, with ARR1 appearing to bear the most critical function among the three proteins. In agreement with these findings, a comparative genome-wide analysis of the leaves of arr1,10,12 and WT plants under both normal and dehydration conditions suggested a cytokinin (CK) signaling-mediated network controlling plant adaptation to drought via many dehydration/droughtand/or ABA-responsive genes that can provide osmotic adjustment and protection to cellular and membrane structures. Expression of all three ARR genes was repressed by dehydration and ABA treatments, inferring that plants down-regulate these genes as an adaptive mechanism to survive drought. Collectively, our results demonstrate that repression of CK response, and thus CK signaling, is one of the strategies plants use to cope with water deficit, providing novel insight for the design of drought-tolerant plants by genetic engineering.cytokinin signaling | drought adaption | comparative transcriptome analysis | type B response regulators

Genome sequencing and population genomic analyses provide insights into the adaptive landscape of silver birch

“…We identified in our sweep list the birch ortholog of Arabidopsis transcription factor ARR1, a key regulator of Arabidopsis root meristem size 66 that mediates the balance between cell division and differentiation by integrating auxin and cytokinin responses. ARR1 is involved in cold-induced inhibition of root growth and reduced auxin accumulation 67 , and it also controls Arabidopsis drought susceptibility 68 . This may explain the link to the geographic and temperature variables detected here.…”

The Role and Regulation of ABI5 (ABA-Insensitive 5) in Plant Development, Abiotic Stress Responses and Phytohormone Crosstalk

“…A triple mutant in the genes encoding the B-type of ARRs, arr1/arr10/arr12 showed an ABA-hypersensitive reaction. Additionally, it was described as drought tolerant, because of the smaller stomatal aperture, a higher anthocyanin biosynthesis and better cell membrane integrity (Nguyen et al, 2016). The A-type negative regulators, ARR4, ARR5 and ARR6, were shown to down-regulate ABI5 expression during seed germination.…”

Cytokinin activity increases stomatal density and transpiration rate in tomato

“…Nishiyama et al (2011) showed that Arabidopsis mutated in the central CK-biosynthesis genes ISOPENTENYL TRANSFERASES ( IPT s) exhibit better survival rates under drought stress. Similarly, Arabidopsis mutants in CK-signaling components—His-kinase receptors, His phosphotransfer proteins, and type-B RRs—exhibit increased tolerance to drought (Kang et al , 2012; Kumar and Verslues, 2015; Nguyen et al , 2016; Nishiyama et al , 2011, 2013; Tran et al , 2007). On the other hand, Kang et al (2012) reported that Arabidopsis plants grown on CK-containing media are less sensitive to drought, exhibiting higher survival rates under these conditions.…”