The DELLA Proteins Interact with MYB21 and MYB24 to Regulate Filament Elongation in Arabidopsis
Gibberellin (GA) and jasmonate (JA) are two essential phytohormones for filament elongation in Arabidopsis . GA and JA trigger degradation of DELLAs and JASMONATE ZIM-domain (JAZ) proteins through SCF SLY1 and SCF COI1 separately to activate filament elongation . In JA pathway, JAZs interact with MYB21 and MYB24 to control filament elongation. However, little is known how DELLAs regulate filament elongation. Results: Here we showed that DELLAs interact with MYB21 and MYB24, and that R2R3
... nd that R2R3 domains of MYB21 and MYB24 are responsible for interaction with DELLAs. Furthermore, we demonstrated that DELLA and JAZ proteins coordinately repress the transcriptional function of MYB21 and MYB24 to inhibit filament elongation . Conclusion: We discovered that DELLAs interact with MYB21 and MYB24, and that DELLAs and JAZs attenuate the transcriptional function of MYB21 and MYB24 to control filament elongation. This study reveals a novel cross-talk mechanism of GA and JA in the regulation of filament elongation in Arabidopsis . Keywords: Gibberellin, Jasmonate, MYB21, MYB24, Filament elongation Background Stamen, comprising a filament and an anther, is one of the plant reproductive organs. Disruptions in stamen development, such as in filament elongation, anther dehiscence, or pollen maturation, can cause male sterility [1, 2]. Numerous studies revealed that these processes are controlled by phytohormones, including jasmonate (JA) and gibberellin (GA) [3, 4]. JAs, including jasmonic acid and its oxylipin derivatives, play key roles in the regulation of plant developmental processes, such as root growth , stamen development , trichome initiation [7, 8], flowering , leaf senescence [10, 11], and apical hook formation [12-14], and as well as control diverse defense responses to abiotic and biotic stresses [15-21]. JAs are perceived by F-box protein CORONATINE INSENSITIVE 1 (COI1) [22, 23],and subsequently induce the degradation of JASMONATE ZIM-DOMAIN (JAZ) proteins [24-26]. Mutants in Arabidopsis JA biosynthesis and signaling transduction, such as defective in anther dehiscence 1 (dad1), 13-lipoxygenase 3/4 (lox3 lox4), 12oxophytodienoate reductase 3 (opr3), coi1-1, or overexpressing the JAZ dominant forms JAZ1△3A or JAZ10.4 lead to deficiency in late stamen development, including filament elongation, anther of a MYC5-SRDX chimeric repressor. Plant J 2015, 81(6):849-860. 38. Qi T, Huang H, Song S, Xie D: Regulation of Jasmonate-Mediated Stamen Development and Seed Production by a bHLH-MYB Complex in Arabidopsis. Plant Cell 2015, 27:1-15. 39. The gibberellic acid signaling repressor RGL2 inhibits Arabidopsis seed germination by stimulating abscisic acid synthesis and ABI5 activity. Plant Cell 2008, 20(10):2729-2745. 40. Kato J: Effect of Gibberellin on Elongation, Water Uptake, and Respiration of Pea-Stem Sections. Science 1956, 123(3208):1132. 41. Pedraz JM, Kircher S et al: Coordinated regulation of Arabidopsis thaliana development by light and gibberellins. Nature 2008, 451(7177):475-479. 42. De Lucas M, Daviere JM, Rodriguez-Falcon M, Pontin M, Iglesias-Pedraz JM, Lorrain S, Fankhauser C, Blazquez MA, Titarenko E, Prat S: A molecular framework for light and gibberellin control of cell elongation. Nature 2008, 451(7177):480-484. 43.