BR Signal Influences Arabidopsis Ovule and Seed Number through Regulating Related Genes Expression by BZR1

Abstract

Ovule and seed developments are crucial processes during plant growth, which are affected by different signaling pathways. In this paper, we demonstrate that the brassinosteroid (BR) signal is involved in ovule initiation and development. Ovule and seed numbers are significantly different when comparing BR-related mutants to wild-type controls. Detailed observation indicates that BR regulates the expression level of genes related to ovule development, including HLL, ANT, and AP2, either directly by targeting the promoter sequences or indirectly via regulation by BR-induced transcription factor BZR1. Also, Western blot demonstrates that the dephosphorylation level of BZR1 is consistent with ovule and seed number. The intragenic bzr1-1D suppressors bzs247 and bzs248 have much fewer ovules and seeds than bzr1-1D, which are similar to wild-type, suggesting that the phenotype can be rescued. The molecular and genetic experiments confirm that BZR1 and AP2 probably affect Arabidopsis ovule number determination antagonistically.

Brassinosteroid Regulates Seed Size and Shape in Arabidopsis

“…We confirmed that AP2 expression was repressed by BR signaling (Huang et al, 2012), and our results showed that AP2 might also regulate BR synthesis or signaling. The expression levels of the BR biosynthetic genes DWF4 and CPD were decreased in the ap2 mutants (Supplemental Fig.…”

“…Seeds produced from ap2-5 bzr1-1D (Huang et al, 2012) and ap2-6 bzr1-1D double mutants were significantly heavier and larger than those of bzr1-1D mutants and were not obviously different than those of ap2-5 and ap2-6 mutants, respectively (Fig. 5, A, B, and E).…”

“…There is no significant difference in seed weight, area, and shape between bzr1-1D and the wild type. We statistically analyzed bzr1-1D seed phenotypes in different grow places and found that the bzr1-1D seed area and weight might be slightly lower than the wild type under poor conditions in some instances, which could be explained by feedback inhibition to BR biosynthesis genes (He et al, 2005), too many seeds per silique (Huang et al, 2012), or the putative function of BZR1/BES1 in seed development (Yu et al, 2011). We did not analyze bes1-D in this work because many important seed developmentregulating genes, such as SHB1-MINI3-IKU2, AP2, and ARF2, were not identified as direct target genes of BES1.…”

Differential expression of the brassinosteroid receptor-encoding BRI1 gene in Arabidopsis

“…4c, d) is accompanied by enhanced CYP85A2 expression (Castle et al 2005), and concomitant induction of the genes that encode the BRI1 and CYP85 orthologues has also been observed in germinating pea (Pisum sativum) (Nomura et al 2007). BRs have an important role in seed and fruit development (Huang et al 2013), and combined mRNA and BR analyses in various dicot species revealed that induction of the CYP85 genes during these processes results in transient accumulation of bioactive BRs (Montoya et al 2005;Nomura et al 2005Nomura et al , 2007Symons et al 2006). Taken together, these results support the notion that local induction of BR biosynthesis, and the resulting accumulation of the hormone, tends to coincide with enhanced BRI1 expression.…”

Molecular basis of fruit development

“…The interactions between the primordial and boundary regions, as well as cytokinin regulation are required for the proper expression and localization of the PIN-FORMED1 (PIN1) auxin transporter and thus for proper auxin fluxes. Brassinosteroid signaling is proposed to support ovule initiation through the stimulation of ANT activity in ovule primordia (Huang et al, 2013;Cucinotta et al, 2014).…”