title: MAX2 affects multiple hormones to promote photomorphogenesis.
abstract: Ubiquitin-26S proteasome system (UPS) has been shown to play central roles in light and hormone-regulated plant growth and development. Previously, we have shown that MAX2, an F-box protein, positively regulates facets of photomorphogenic development in response to light. However, how MAX2 controls these responses is still unknown. Here, we show that MAX2 oppositely regulates GA and ABA biosynthesis to optimize seed germination in response to light. Dose-response curves showed that max2 seeds are hyposensitive to GA and hypersensitive to ABA in seed germination responses. RT-PCR assays demonstrated that the expression of GA biosynthetic genes is down-regulated, while the expression of GA catabolic genes is up-regulated in the max2 seeds compared to wild-type. Interestingly, expression of both ABA biosynthetic and catabolic genes is up-regulated in the max2 seeds compared to wild-type. Treatment with an auxin transport inhibitor, NPA, showed that increased auxin transport in max2 seedlings contributes to the long hypocotyl phenotype under light. Moreover, light-signaling phenotypes are restricted to max2, as the biosynthetic mutants in the strigolactone pathway, max1, max3, and max4, did not display any defects in seed germination and seedling de-etiolation compared to wild-type. Taken together, these data suggest that MAX2 modulates multiple hormone pathways to affect photomorphogenesis.
authors.affiliation: Section of Molecular Cell and Developmental Biology and the Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, TX 78712, USA.
authors.forename: Hui
authors.initials: H
authors.lastname: Shen
authors.forename: Ling
authors.initials: L
authors.lastname: Zhu
authors.forename: Qing-Yun
authors.initials: QY
authors.lastname: Bu
authors.forename: Enamul
authors.initials: E
authors.lastname: Huq
mesh_terms: D000040:Abscisic Acid / Q000494:pharmacology; D017360:Arabidopsis / Q000187:drug effects / Q000254:growth & development* / Q000528:radiation effects*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D001692:Biological Transport / Q000187:drug effects / Q000528:radiation effects; D053898:Biosynthetic Pathways / Q000187:drug effects / Q000528:radiation effects; D002352:Carrier Proteins / Q000378:metabolism*; D004843:Epistasis, Genetic / Q000187:drug effects / Q000528:radiation effects; D018506:Gene Expression Regulation, Plant / Q000187:drug effects / Q000528:radiation effects; D017343:Genes, Plant / Q000235:genetics; D018525:Germination / Q000187:drug effects / Q000528:radiation effects; D005875:Gibberellins / Q000494:pharmacology; D007210:Indoleacetic Acids / Q000378:metabolism; D007783:Lactones / Q000494:pharmacology; D008027:Light; D009024:Morphogenesis / Q000187:drug effects / Q000528:radiation effects*; D009154:Mutation / Q000235:genetics; D009928:Organ Specificity / Q000187:drug effects / Q000528:radiation effects; D010641:Phenotype; D010937:Plant Growth Regulators / Q000378:metabolism*; D036226:Seedlings / Q000187:drug effects / Q000254:growth & development / Q000528:radiation effects; D012639:Seeds / Q000187:drug effects / Q000254:growth & development / Q000528:radiation effects; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D002352:Carrier Proteins; D005875:Gibberellins; D007210:Indoleacetic Acids; D007783:Lactones; C435920:MAX2 protein, Arabidopsis; D010937:Plant Growth Regulators; D000040:Abscisic Acid; C471983:AT2G32950 protein, Arabidopsis; D044767:Ubiquitin-Protein Ligases