AUXIN RESPONSE FACTOR17 Is Essential for Pollen Wall Pattern Formation in Arabidopsis      

Abstract

In angiosperms, pollen wall pattern formation is determined by primexine deposition on the microspores. Here, we show that AUXIN RESPONSE FACTOR17 (ARF17) is essential for primexine formation and pollen development in Arabidopsis (Arabidopsis thaliana). The arf17 mutant exhibited a male-sterile phenotype with normal vegetative growth. ARF17 was expressed in microsporocytes and microgametophytes from meiosis to the bicellular microspore stage. Transmission electron microscopy analysis showed that primexine was absent in the arf17 mutant, which leads to pollen wall-patterning defects and pollen degradation. Callose deposition was also significantly reduced in the arf17 mutant, and the expression of CALLOSE SYNTHASE5 (CalS5), the major gene for callose biosynthesis, was approximately 10% that of the wild type. Chromatin immunoprecipitation and electrophoretic mobility shift assays showed that ARF17 can directly bind to the CalS5 promoter. As indicated by the expression of DR5-driven green fluorescent protein, which is an synthetic auxin response reporter, auxin signaling appeared to be specifically impaired in arf17 anthers. Taken together, our results suggest that ARF17 is essential for pollen wall patterning in Arabidopsis by modulating primexine formation at least partially through direct regulation of CalS5 gene expression.

Phosphorylation of ARF2 Relieves Its Repression of Transcription of the K+ Transporter Gene HAK5 in Response to Low Potassium Stress

“…According to their functions, these ARFs are divided into two classes: transcriptional activators and transcriptional repressors (Guilfoyle and Hagen, 2007). Many investigations have revealed the essential roles of ARFs in plant growth and development as well as in stress adaptation (Hardtke and Berleth, 1998;Nemhauser et al, 2000;Ellis et al, 2005;Okushima et al, 2005aOkushima et al, , 2005bWang et al, 2011;Yang et al, 2013). In this study, we demonstrate that ARF2 participates in the regulation of K + uptake.…”

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].…”

Anther and pollen development: A conserved developmental pathway

“…ARF17 , an auxin responsive factor, plays a major role in plant fertility by regulating primexine deposition. The arf17 mutant shows defective callose formation, a total absence of primexine and pollen degeneration (Yang et al ). In addition, it has been demonstrated that ARF17 directly regulates CalS5expression (Yang et al ).…”

“…The arf17 mutant shows defective callose formation, a total absence of primexine and pollen degeneration (Yang et al ). In addition, it has been demonstrated that ARF17 directly regulates CalS5expression (Yang et al ). CalS5 expression is also reduced in the defective in exine formation1 ( dex1) mutant; this gene encodes for a plasma membrane protein, which is highly conserved in higher plants such as rice, barley and Brachypodium (Ma et al ) (Table ).…”