title: Regulation of drought tolerance by the F-box protein MAX2 in Arabidopsis.
abstract: MAX2 (for MORE AXILLARY GROWTH2) has been shown to regulate diverse biological processes, including plant architecture, photomorphogenesis, senescence, and karrikin signaling. Although karrikin is a smoke-derived abiotic signal, a role for MAX2 in abiotic stress response pathways is least investigated. Here, we show that the max2 mutant is strongly hypersensitive to drought stress compared with wild-type Arabidopsis (Arabidopsis thaliana). Stomatal closure of max2 was less sensitive to abscisic acid (ABA) than that of the wild type. Cuticle thickness of max2 was significantly thinner than that of the wild type. Both of these phenotypes of max2 mutant plants correlate with the increased water loss and drought-sensitive phenotype. Quantitative real-time reverse transcription-polymerase chain reaction analyses showed that the expression of stress-responsive genes and ABA biosynthesis, catabolism, transport, and signaling genes was impaired in max2 compared with wild-type seedlings in response to drought stress. Double mutant analysis of max2 with the ABA-insensitive mutants abi3 and abi5 indicated that MAX2 may function upstream of these genes. The expression of ABA-regulated genes was enhanced in imbibed max2 seeds. In addition, max2 mutant seedlings were hypersensitive to ABA and osmotic stress, including NaCl, mannitol, and glucose. Interestingly, ABA, osmotic stress, and drought-sensitive phenotypes were restricted to max2, and the strigolactone biosynthetic pathway mutants max1, max3, and max4 did not display any defects in these responses. Taken together, these results uncover an important role for MAX2 in plant responses to abiotic stress conditions.
authors.affiliation: Northeast Institute of Geography and Agroecology, Key Laboratory of Soybean Molecular Design Breeding, Chinese Academy of Sciences, Harbin 150081, China.
authors.forename: Qingyun
authors.initials: Q
authors.lastname: Bu
authors.forename: Tianxiao
authors.initials: T
authors.lastname: Lv
authors.forename: Hui
authors.initials: H
authors.lastname: Shen
authors.forename: Phi
authors.initials: P
authors.lastname: Luong
authors.forename: Jimmy
authors.initials: J
authors.lastname: Wang
authors.forename: Zhenyu
authors.initials: Z
authors.lastname: Wang
authors.forename: Zhigang
authors.initials: Z
authors.lastname: Huang
authors.forename: Langtao
authors.initials: L
authors.lastname: Xiao
authors.forename: Cawas
authors.initials: C
authors.lastname: Engineer
authors.forename: Tae Houn
authors.initials: TH
authors.lastname: Kim
authors.forename: Julian I
authors.initials: JI
authors.lastname: Schroeder
authors.forename: Enamul
authors.initials: E
authors.lastname: Huq
mesh_terms: D000040:Abscisic Acid / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D017360:Arabidopsis / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D055864:Droughts; D044783:F-Box Proteins / Q000235:genetics / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D018525:Germination; D009154:Mutation; D054046:Plant Stomata / Q000187:drug effects; D030821:Plants, Genetically Modified; D036226:Seedlings / Q000235:genetics / Q000254:growth & development; D015398:Signal Transduction / Q000235:genetics; D013312:Stress, Physiological
chemical_list: D029681:Arabidopsis Proteins; D002352:Carrier Proteins; D044783:F-Box Proteins; C435920:MAX2 protein, Arabidopsis; D000040:Abscisic Acid