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

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.

Masks Start to Drop: Suppressor of MAX2 1-Like Proteins Reveal Their Many Faces

“…In addition, SMXL4/5, but not SMXL3, regulate secondary phloem development during radial growth, pointing to a possible functional distinction between the SMXL3 and SMXL4/5 clade ( Shi et al, 2019 ; Wallner et al, 2020 ). SMXL4 also plays additional roles in gibberellic acid- and light-dependent regulation of flowering and seed setting, as well as in drought stress tolerance ( Yang et al, 2015 , 2016 , 2020b ). Contrary to other SMXL family members in Arabidopsis , SMXL3/4/5 are not involved in either KL or SL signaling and are not subjected to MAX2-dependent degradation ( Wallner et al, 2017 ).…”

HOP co-chaperones contribute to GA signaling by promoting the accumulation of the F-box protein SNE in Arabidopsis

“…The number of days required by each plant for bolting initiation (observed as a rapid elongation of the stem) was scored and quantified. GA treatments were carried out as described in Yang et al. (2020) .…”

Environmental regulation of male fertility is mediated through Arabidopsis transcription factors bHLH89, 91, and 10

“…Light is known to influence male reproductive development in terms of day length and the duration of light exposure, but additionally light intensity has been shown to affect the initiation of flowering via phytochrome-mediated pathways involving PHYTOCHROME INTERACTING FACTORS (PIFs), a class of bHLH proteins ( Franklin, 2008 ; Wit et al , 2016 ). There have been few studies into the effects of light on reproductive development beyond floral transition; to date, only MYB33, MYB65, YET ANOTHER KINASE1 (YAK1), and HEAT SHOCK PROTEIN-RELATED (HSPR) have a reported link between light and male fertility in Arabidopsis ( Millar and Gubler, 2005 ; Huang et al ., 2017 ; Yang et al , 2020 ). yak1 mutants have shorter siliques and reduced seed number, and this phenotype is intensified under low light intensity (50 µmol m –2 s –1 ; Huang et al ., 2017 ).…”

“…yak1 mutants have shorter siliques and reduced seed number, and this phenotype is intensified under low light intensity (50 µmol m –2 s –1 ; Huang et al ., 2017 ). Likewise, the hspr mutant flowers later, with reduced pollen viability and seed set in low light conditions (20–60 µmol m –2 s –1 ; Yang et al , 2020 ). Anthers from the Arabidopsis GAMYB-Like myb33 myb65 double mutant exhibit a hypertrophic tapetum and a pre-meiotic block in microspore development, resulting in plants that are partially male sterile.…”