BRANCHED1Promotes Axillary Bud Dormancy in Response to Shade inArabidopsis   

Abstract

Plants interpret a decrease in the red to far-red light ratio (R:FR) as a sign of impending shading by neighboring vegetation. This triggers a set of developmental responses known as shade avoidance syndrome. One of these responses is reduced branching through suppression of axillary bud outgrowth. The Arabidopsis thaliana gene BRANCHED1 (BRC1), expressed in axillary buds, is required for branch suppression in response to shade. Unlike wild-type plants, brc1 mutants develop several branches after a shade treatment. BRC1 transcription is positively regulated 4 h after exposure to low R:FR. Consistently, BRC1 is negatively regulated by phytochrome B. Transcriptional profiling of wild-type and brc1 buds of plants treated with simulated shade has revealed groups of genes whose mRNA levels are dependent on BRC1, among them a set of upregulated abscisic acid response genes and two networks of cell cycle– and ribosome-related downregulated genes. The downregulated genes have promoters enriched in TEOSINTE BRANCHED1, CYCLOIDEA, and PCF (TCP) binding sites, suggesting that they could be transcriptionally regulated by TCP factors. Some of these genes respond to BRC1 in seedlings and buds, supporting their close relationship with BRC1 activity. This response may allow the rapid adaptation of plants to fluctuations in the ratio of R:FR light.

ABA receptor PYL9 promotes drought resistance and leaf senescence

“…ABA accumulates in polar apical buds during short-day conditions, which may contribute to growth suppression and maintenance of dormancy (36). Of 146 BRC1-dependent bud dormancy genes that are putatively involved in shade-induced axillary bud dormancy, 78 are regulated during senescence (35,37,38). Strikingly, master positive regulators of senescence, such as ORE1, AtNAP, and MAX2/ORE9, are also upregulated during bud dormancy, suggesting that bud dormancy is coordinated with leaf senescence to contribute to stress resistance.…”

“…Strikingly, master positive regulators of senescence, such as ORE1, AtNAP, and MAX2/ORE9, are also upregulated during bud dormancy, suggesting that bud dormancy is coordinated with leaf senescence to contribute to stress resistance. Most of these bud dormancy genes contain a CACGTGt motif in their promoters (37), which is recognized by ABA-related basic region-leucine zipper (b-ZIP) transcription factors (39).…”

Transcriptome Profiling of Tiller Buds Provides New Insights into PhyB Regulation of Tillering and Indeterminate Growth in Sorghum

“…The level of CK in the stem is reduced by auxinmediated suppression of a key CK biosynthesis gene, whereas ABA appears to inhibit bud outgrowth independently of auxin (Chatfield et al, 2000;Tanaka et al, 2006;Beveridge et al, 2009). Exposure of Arabidopsis to low R/FR illumination repressed bud outgrowth and increased expression of genes involved in ABA biosynthesis and signaling in buds (González-Grandío et al, 2013;Reddy et al, 2013). The expression of these genes was decreased when buds were stimulated to grow by R light.…”

“…Inhibition of bud outgrowth by FR in Arabidopsis has been linked to an increase in the expression of ABA biosynthesis and signaling genes and ABA level (González-Grandío et al, 2013;Reddy et al, 2013). Analysis of differentially expressed genes in phyB-1/ wild-type buds identified several changes in gene expression related to ABA synthesis or signaling between 6 DAP and 8 DAP (Fig.…”

“…S7). In pea and Arabidopsis, the expression of genes encoding ribosomal protein genes is lower in dormant buds (Devitt and Stafstrom, 1995;González-Grandío et al, 2013).…”