DELLA activity is required for successful pollen development in the Columbia ecotype of Arabidopsis

Abstract

Excessive gibberellin (GA) signalling, mediated through the DELLA proteins, has a negative impact on plant fertility. Loss of DELLA activity in the monocot rice (Oryza sativa) causes complete male sterility, but not in the dicot model Arabidopsis (Arabidopsis thaliana) ecotype Landsberg erecta (Ler), in which DELLA function has been studied most extensively, leading to the assumption that DELLA activity is not essential for Arabidopsis pollen development. A novel DELLA fertility phenotype was identified in the Columbia (Col-0) ecotype that necessitates re-evaluation of the general conclusions drawn from Ler. Fertility phenotypes were compared between the Col-0 and Ler ecotypes under conditions of chemical and genetic GA overdose, including mutants in both ecotypes lacking the DELLA paralogues REPRESSOR OF ga1-3 (RGA) and GA INSENSITIVE (GAI). Ler displays a less severe fertility phenotype than Col-0 under GA treatment. Col-0 rga gai mutants, in contrast with the equivalent Ler phenotype, were entirely male sterile, caused by post-meiotic defects in pollen development, which were rescued by the reintroduction of DELLA into either the tapetum or developing pollen. We conclude that DELLA activity is essential for Arabidopsis pollen development. Differences between the fertility responses of Col-0 and Ler might be caused by differences in downstream signalling pathways or altered DELLA expression.

Genetic and Biochemical Mechanisms of Pollen Wall Development

“…AUXIN RESPONSE FACTOR 17 (ARF17) controls callose biosynthesis and primexine deposition by directly modulating the expression of CalS5 and RPG1 [102]. In flowering plants, GA regulates pollen wall development via GAMYB [81,84], and GAMYB activates targets such as CYP703A3 [81], and the double mutant rga-28 gai-td1, which is defective in the key GA signaling repressor DELLA proteins, displays defective pollen wall development [103]. Cytokinin receptors in the sporophyte are indispensable for pollen maturation [104], and loss of function of ROCK1 (REPRESSOR OF CYTOKININ DEFICIENCY 1) enhances cytokinin response and induces defective exine formation [67].…”

Transcriptomic Analysis Implies That GA Regulates Sex Expression via Ethylene-Dependent and Ethylene-Independent Pathways in Cucumber (Cucumis sativus L.)

“…In addition, GA signaling pathway is involved in stamen and anther development in hermaphroditic plants, such as Arabidopsis and rice ( Oryza sativa ) (Cheng et al, 2004; Fleet and Sun, 2005; Aya et al, 2009; Sun, 2010, 2011; Plackett et al, 2011; Song et al, 2013). In this pathway, GA first binds with GID1 receptor and promotes the interaction between GID1 and DELLA proteins (repressors of GA signaling), leading to a rapid degradation of DELLA proteins by an ubiquitin-proteasome pathway, and the proteolysis of DELLA proteins releases their inhibitory effect on GA action and allows plant growth and development (Fleet and Sun, 2005; Murase et al, 2008; Harberd et al, 2009; Sun, 2010, 2011; Plackett et al, 2014). GAMYB is a positive regulator in GA signaling pathway and acts as an important downstream gene of DELLA proteins (Olszewski et al, 2002; Achard et al, 2004; Fleet and Sun, 2005).…”

NO FLOWERING IN SHORT DAY (NFL) is a bHLH transcription factor that promotes flowering specifically under short-day in Arabidopsis

“…The rga-28 (Tyler et al, 2004), gai-td2 (Plackett et al, 2014) and rgl1-SK62 (Park et al, 2013) mutants have been described. The rgl2 mutant was isolated from the Arabidopsis Biological Resource Center (SAIL_345).…”