Abscisic Acid Regulates Early Seed Development in Arabidopsis by ABI5-Mediated Transcription of SHORT HYPOCOTYL UNDER BLUE1

Abstract

Seed development includes an early stage of endosperm proliferation and a late stage of embryo growth at the expense of the endosperm in Arabidopsis thaliana. Abscisic acid (ABA) has known functions during late seed development, but its roles in early seed development remain elusive. In this study, we report that ABA-deficient mutants produced seeds with increased size, mass, and embryo cell number but delayed endosperm cellularization. ABSCISIC ACID DEFICIENT2 (ABA2) encodes a unique short-chain dehydrogenase/reductase that functions in ABA biosynthesis, and its expression pattern overlaps that of SHORT HYPOCOTYL UNDER BLUE1 (SHB1) during seed development. SHB1 RNA accumulation was significantly upregulated in the aba2-1 mutant and was downregulated by the application of exogenous ABA. Furthermore, RNA accumulation of the basic/region leucine zipper transcription factor ABSCISIC ACID-INSENSITIVE5 (ABI5), involved in ABA signaling, was decreased in aba2-1. Consistent with this, seed size was also increased in abi5. We further show that ABI5 directly binds to two discrete regions in the SHB1 promoter. Our results suggest that ABA negatively regulates SHB1 expression, at least in part, through the action of its downstream signaling component ABI5. Our findings provide insights into the molecular mechanisms by which ABA regulates early seed development.

Global Analysis Reveals the Crucial Roles of DNA Methylation during Rice Seed Development

“…In barley (Hordeum vulgare), decreased ABA content causes abnormal endosperm development, including abnormal cellularization/ differentiation of endosperm (Sreenivasulu et al, 2010). Recent studies showed that the ABA-deficient mutant aba2-1 presents delayed endosperm cellularization (Cheng et al, 2014), suggesting that ABA promotes cellularization, which is consistent with our finding revealing the up-regulation of ABA responserelated genes during rice endosperm cellularization. The expression of a DUF1264 domain-containing protein (LOC_Os05g49440) during cellularization is regulated by methylation, and the phosphorylation state of its homolog in Arabidopsis is modulated by ABA (Ghelis et al, 2008), which suggests a possible role of LOC_Os05g49440 in cellularization in response to ABA.…”

Seedlings of large-seeded plants are considered to withstand drought stresses efficiently

“…ARF2 negatively regulates the expression of ANT, consequently ANT directly regulates the function of COR15A to regulate seed mass and stress resistance. The ARF2-ANT-COR15A-ABA-mediated signal cascade that we have identified in this study might be different from that which regulates seed development through the SHB1-ABAmediated pathway, which has been proposed by Cheng et al (2014).…”

“…Studies have identified that the ABA2, ABI5 and SHB1 genes are involved in controlling seed size (Cheng et al, 2014). Specifically, ABA2 is positively regulated upon ABA accumulation, activating ABI5 in ABA signaling, consequently negatively modulating SHB1 The intensity of GUS coloration was quantified by using Adobe Photoshop CS (Adobe Systems) software, as described by Wang et al (2011).…”

Type-B ARABIDOPSIS RESPONSE REGULATORs Specify the Shoot Stem Cell Niche by Dual Regulation of WUSCHEL

“…SAB5300167). Finally, the precipitated DNA fragments were analyzed using RT-qPCR as described previously (Cheng et al, 2014;Zhou et al, 2009). Tissues derived from different plants were used in distinct biological replicates.…”