The Role of GAMYB Transcription Factors in GA-Regulated Gene Expression

Woodger, Fiona J.; Millar, Anthony A.; Murray, Fiona; Jacobsen, John V.; Gubler, Frank

doi:10.1007/s00344-003-0025-8

Cited by 89 publications

(68 citation statements)

References 52 publications

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“…Functions such as this would be consistent with the secretory role of the aleurone and its final progression to PCD through autophagy (Fath et al, 2000). All these data strongly support the notion that the GAMYB class of transcription factors are positive regulators of GA signaling during seed germination (Gubler et al, 1995;Woodger et al, 2003). Finally, the function of these GAMYB transcription factors is highly conserved, as many common homologs are up-regulated by GAMYB in mir159ab vegetative tissues and in anthers and embryoless half seeds of rice (Table I; Tsuji et al, 2006).…”

Section: Table I Transcript Profiling In Mir159ab Plantssupporting

confidence: 71%

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The MicroRNA159-Regulated GAMYB-like Genes Inhibit Growth and Promote Programmed Cell Death in Arabidopsis

et al. 2010

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The microRNA159 (miR159) family represses the conserved GAMYB-like genes that encode R2R3 MYB domain transcription factors that have been implicated in gibberellin (GA) signaling in anthers and germinating seeds. In Arabidopsis (Arabidopsis thaliana), the two major miR159 family members, miR159a and miR159b, are functionally specific for two GAMYB-like genes, MYB33 and MYB65. These transcription factors have been shown to be involved in anther development, but there are differing reports about their role in the promotion of flowering and little is known about their function in seed germination. To understand the function of this pathway, we identified the genes and processes controlled by these GAMYB-like genes. First, we demonstrate that miR159 completely represses MYB33 and MYB65 in vegetative tissues. We show that GA does not release this repression and that these transcription factors are not required for flowering or growth. By contrast, in the absence of miR159, the deregulation of MYB33 and MYB65 in vegetative tissues up-regulates genes that are highly expressed in the aleurone and GA induced during seed germination. Confirming that these genes are GAMYB-like regulated, their expression was reduced in myb33.myb65.myb101 seeds. Aleurone vacuolation, a GA-mediated programmed cell death process required for germination, was impaired in these seeds. Finally, the deregulation of MYB33 and MYB65 in vegetative tissues inhibits growth by reducing cell proliferation. Therefore, we conclude that miR159 acts as a molecular switch, only permitting the expression of GAMYB-like genes in anthers and seeds. In seeds, these transcription factors participate in GA-induced pathways required for aleurone development and death.

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Section: Table I Transcript Profiling In Mir159ab Plantssupporting

confidence: 71%

“…The GAMYB or GAMYB-like genes encode a highly conserved family of R2R3 MYB domain transcription factors that have been implicated in GA signal transduction (Woodger et al, 2003). GAMYB was initially identified in the cereal aleurone, where its expression is induced by GA (Gubler et al, 1995).…”

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confidence: 99%

The MicroRNA159-Regulated GAMYB-like Genes Inhibit Growth and Promote Programmed Cell Death in Arabidopsis

et al. 2010

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“…Three CESA promoter fragments were significantly enriched in MYB61 Ox plants ( Figure 5F). Sequence searching within the bound fragments identified a conserved element annotated as GAMYB, a motif bound by GA-responsive MYBs (Woodger et al, 2003). Then, 34-bp oligonucleotides containing a wild-type motif and a single base-mutated motif (GAMYB and GAMYBm; Supplemental Figure 6E) were synthesized.…”

Section: Myb61 Directly Activated By Nac29/31 Targets Gamyb Motifs Ofmentioning

confidence: 99%

“…Moreover, this signaling mechanism was found to be conserved in land plants, as evidenced by the following observations: the Arabidopsis DELLA protein RGA interacts with SND1; the Arabidopsis GA-related mutants exhibit alterations in CESA expression and cellulose synthesis; and the CESAs from Arabidopsis and poplar were GA-inducible and have at least one GAMYB element in their promoter regions. GAMYB binding proteins are TFs belonging to a distinct subclass in the MYB superfamily, which is widely present in plant species, and in which many members are required for modulating cell wall biosynthesis (Woodger et al, 2003;Zhong and Ye, 2007). Therefore, the GA-response pathway mediated by GAMYB binding TFs, such as MYB61, is applicable to other plant species.…”

Section: Ga Regulates Secondary Wall Cellulose Synthesis Via An Slr1-mentioning

confidence: 99%

A Gibberellin-Mediated DELLA-NAC Signaling Cascade Regulates Cellulose Synthesis in Rice

et al. 2015

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Cellulose, which can be converted into numerous industrial products, has important impacts on the global economy. It has long been known that cellulose synthesis in plants is tightly regulated by various phytohormones. However, the underlying mechanism of cellulose synthesis regulation remains elusive. Here, we show that in rice (Oryza sativa), gibberellin (GA) signals promote cellulose synthesis by relieving the interaction between SLENDER RICE1 (SLR1), a DELLA repressor of GA signaling, and NACs, the top-layer transcription factors for secondary wall formation. Mutations in GA-related genes and physiological treatments altered the transcription of CELLULOSE SYNTHASE genes (CESAs) and the cellulose level. Multiple experiments demonstrated that transcription factors NAC29/31 and MYB61 are CESA regulators in rice; NAC29/31 directly regulates MYB61, which in turn activates CESA expression. This hierarchical regulation pathway is blocked by SLR1-NAC29/31 interactions. Based on the results of anatomical analysis and GA content examination in developing rice internodes, this signaling cascade was found to be modulated by varied endogenous GA levels and to be required for internode development. Genetic and gene expression analyses were further performed in Arabidopsis thaliana GA-related mutants. Altogether, our findings reveal a conserved mechanism by which GA regulates secondary wall cellulose synthesis in land plants and provide a strategy for manipulating cellulose production and plant growth.

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“…Some recent studies have suggested that GAMYB may be involved in other GA-regulated events, such as floral initiation, stem elongation, anther development, and seed development (reviewed by Woodger et al, 2003). For example, GAMYB is expressed at a high level in the floral meristems at the double-ridge stage and in stamen primordia of the grass L. temulentum .…”

Section: Introductionmentioning

confidence: 99%

Loss-of-Function Mutations of the Rice GAMYB Gene Impair α-Amylase Expression in Aleurone and Flower Development

et al. 2003

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GAMYB was first isolated as a positive transcriptional regulator of gibberellin (GA)-dependent ␣ -amylase expression in barley aleurone cells, and its molecular and biochemical properties have been well characterized. However, the role of GAMYB elsewhere in the plant is not well understood. To investigate the molecular function of GAMYB outside of the aleurone cells, we isolated loss-of-function mutants from a panel of rice mutants produced by the insertion of a retrotransposon, Tos17 . Through PCR screening using primers for rice GAMYB ( OsGAMYB ) and Tos17 , we isolated three independent mutant alleles that contained Tos17 inserted in the exon region. No ␣ -amylase expression in the endosperm was induced in these mutants in response to GA treatment, indicating that the Tos17 insertion had knocked out OsGAMYB function. We found no significant defects in the growth and development of the mutants at the vegetative stage. After the phase transition to the reproductive stage, however, shortened internodes and defects in floral organ development, especially a defect in pollen development, were observed. On the other hand, no difference was detected in flowering time. High-level OsGAMYB expression was detected in the aleurone cells, inflorescence shoot apical region, stamen primordia, and tapetum cells of the anther, but only low-level expression occurred in organs at the vegetative stage or in the elongating stem. These results demonstrate that, in addition to its role in the induction of ␣ -amylase in aleurone, OsGAMYB also is important for floral organ development and essential for pollen development.

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The Role of GAMYB Transcription Factors in GA-Regulated Gene Expression

Cited by 89 publications

References 52 publications

The MicroRNA159-Regulated GAMYB-like Genes Inhibit Growth and Promote Programmed Cell Death in Arabidopsis

The MicroRNA159-Regulated GAMYB-like Genes Inhibit Growth and Promote Programmed Cell Death in Arabidopsis

A Gibberellin-Mediated DELLA-NAC Signaling Cascade Regulates Cellulose Synthesis in Rice

Loss-of-Function Mutations of the Rice GAMYB Gene Impair α-Amylase Expression in Aleurone and Flower Development

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