AtbHLH68 transcription factor contributes to the regulation of ABA homeostasis and drought stress tolerance in Arabidopsis thaliana

Rozenn Le Hir (1, 2) , Mathieu Castelain (3) , Dipankar Chakraborti (3) , Thomas Moritz (3) , Sylvie Dinant (1) , Catherine Bellini (1, 4)

1 IJPB - Institut Jean-Pierre Bourgin
2 IJPB - Institut Jean-Pierre Bourgin
3 UPSC - Umea Plant Science Center
4 Umeå Plant Science Centre, Department of Plant Physiology

Basic helix-loop-helix (bHLH) transcription factors are involved in a wide range of developmental processes and in response to biotic and abiotic stresses. They represent one of the biggest families of transcription factors but only few of them have been functionally characterized. Here we report the characterization of AtbHLH68 and show that, although the knock out mutant did not have an obvious development phenotype, it was slightly more sensitive to drought stress than the Col-0, and AtbHLH68 overexpressing lines displayed defects in lateral root (LR) formation and a significant increased tolerance to drought stress, likely related to an enhanced sensitivity to abscisic acid (ABA) and/or increased ABA content. AtbHLH68 was expressed in the vascular system of Arabidopsis and its expression was modulated by exogenously applied ABA in an organ-specific manner. We showed that the expression of genes involved in ABA metabolism [AtAAO3 (AtALDEHYDE OXIDASE 3) and AtCYP707A3 (AtABSCISIC ACID 8′HYDROXYLASE 3)], in ABA-related response to drought-stress (AtMYC2, AtbHLH122 and AtRD29A) or during LRs development (AtMYC2 and AtABI3) was de-regulated in the overexpressing lines. We propose that AtbHLH68 has a function in the regulation of LR elongation, and in the response to drought stress, likely through an ABA-dependent pathway by regulating directly or indirectly components of ABA signaling and/or metabolism.

Mots clés: lateral root primordium NAA; 1-naphthaleneacetic acid PCR; polymerase chain reaction qPCR; quantitative polymerase chain reaction; dichlorophenoxyacetic acid; ABA; abscisic acid; ACC; 1-aminocyclopropane-1carboxylic acid; bHLH; basic HELIX-LOOP-HELIX; BR; brassinosteroid; GA 3; gibberellic acid; LR; lateral root; LRP; lateral root primordium; NAA; 1-naphthaleneacetic acid; PCR; polymerase chain reaction; qPCR; homeostasis; abscissins; Abbreviations -2; 4-D; dichlorophenoxyacetic acid ABA; abscisic acid ACC; 1-aminocyclopropane-1carboxylic acid bHLH; basic HELIX-LOOP-HELIX BR; brassinosteroid GA 3; gibberellic acid LR lateral root LRP

Mots clés: arabidopsis thaliana; transcription; adaptation à la sécheresse; homéostasie; stress à la sécheresse; acide abscisique

Domaines: Sciences du Vivant [q-bio]

Rozenn Le Hir, Mathieu Castelain, Dipankar Chakraborti, Thomas Moritz, Sylvie Dinant, et al.. AtbHLH68 transcription factor contributes to the regulation of ABA homeostasis and drought stress tolerance in Arabidopsis thaliana. Physiologia Plantarum, 2017, 160 (3), pp.312-327. ⟨10.1111/ppl.12549⟩. ⟨hal-01594689⟩