AtHSPR is involved in GA- and light intensity-mediated control of flowering time and seed set in Arabidopsis.

Yan Sun,Lijuan Xuan,Zhiyuan Bian,Guoqiang Yuan,Yuke Lian,Mengya Chen,Tao Yang,Lina Zhou,Frank Wellmer,Yongli Wang,Chongying Wang,Xinyu Wang

doi:10.1093/jxb/eraa128

Abstract

Flowering is a dynamic and synchronized process, the timing of which is finely tuned by various environmental signals. A T-DNA insertion mutant in Arabidopsis HEAT SHOCK PROTEIN-RELATED (AtHSPR) exhibited late-flowering phenotypes under both long-day (LD) and short-day (SD) conditions compared to the wild-type, while over-expression of AtHSPR promoted flowering. Exogenous application of gibberellin (GA) partially rescued the late-flowering mutant phenotype under both LD and SD conditions, suggesting that AtHSPR is involved in GA biosynthesis and/or the GA signaling that promotes flowering. Under SD or low-light conditions, the Athspr mutant exhibited late flowering together with reduced pollen viability and seed set, defective phenotypes that were partially rescued by GA treatment. qRT-PCR assays confirmed that GA biosynthetic genes were down-regulated, that GA catabolic genes were up-regulated, and that the levels of bioactive GA and its intermediates were decreased in Athspr under both SD and low-light/LD, further suggesting that AtHSPR could be involved in the GA pathway under SD and low-light conditions. Furthermore, AtHSPR interacted in vitro with OFP1 and KNAT5, which are transcriptional repressors of GA20ox1 in GA biosynthesis. Taken together, our findings demonstrate that AtHSPR plays a positive role in GA- and light intensity-mediated regulation of flowering and seed set.

Highlights

Different plants have evolved diverse flowering times to adapt to ecological niches
Under short-day (SD) conditions, GA acts as a positive regulator that directly promotes the expression of SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (SOC1) (Moon et al, 2003), which subsequently activates the downstream genes LFY and AP1 to promote flowering.The DELLA proteins REPRESSOR OF GA1-3 (RGA), REPRESSOR OF GA1-3-LIKE 1 (RGL1), and RGL2 repress GA signaling to delay floral development (Cheng et al, 2004;Yu et al, 2004)
The differences were greater under SDs (Fig. 1B, D, F).These results suggested that Arabidopsis thaliana heat shock protein-related (AtHSPR) positively regulated flowering time under LD and SD conditions

Summary

Introduction

Different plants have evolved diverse flowering times to adapt to ecological niches. The change from vegetative to reproductive growth is sophisticatedly controlled by both endogenous developmental cues and external environmental stimuli to maximize reproductive success and seed production.The major pathways regulating flowering time have been widely reported in the model plant Arabidopsis thaliana. The transcription factors KNOX (Class-I KNOTTED1LIKE HOMEOBOX) have been shown to reduce GA levels by promoting the expression the catabolic genes GA2ox and GA2ox or by directly repressing the transcription of the biosynthetic gene GA20ox in the shoot apical meristem (SAM; Sakamoto et al, 2001; Chen et al, 2004; Jasinski et al, 2005).The GA pathway interacts with the photoperiodic pathway to regulate the expression of FT (Hisamatsu and King, 2008;Yamaguchi, 2008; Osnato et al, 2012; Song et al, 2012)

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Discussion

Conclusion