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

Jun Yang,Yue-Feng Guan,Qi-Shi Jia,Jun Zhu,Lei Tian,Ming-Xi Sun,Xue-Yong Huang,Zhong-Nan Yang

doi:10.1104/pp.113.214940

Jun Yang, Yue-Feng Guan + Show 6 more

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https://doi.org/10.1104/pp.113.214940

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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.

Highlights

In angiosperms, pollen wall pattern formation is determined by primexine deposition on the microspores
It was reported that Arabidopsis (Arabidopsis thaliana) CYCLIN-DEPENDENT KINASE G1 (CDKG1) associates with the spliceosome to regulate the CALLOSE SYNTHASE5 (CalS5) pre-mRNA splicing for pollen wall formation (Huang et al, 2013)
Thermal asymmetric interlaced (TAIL)-PCR (Liu et al, 1995) and sequencing of the flanking sequence revealed that a transfer DNA (T-DNA) was inserted in the first exon of the AUXIN RESPONSE FACTOR17 (ARF17) gene (Fig. 2C)

Summary

Introduction

Pollen wall pattern formation is determined by primexine deposition on the microspores. 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. Besides CalS5, four membrane-associated proteins have been reported to be involved in primexine formation: DEFECTIVE EXINE FORMATION1 (DEX1; Paxson-Sowders et al, 1997, 2001), NO EXINE FORMATION1 (NEF1; Ariizumi et al, 2004), RUPTURED POLLEN GRAIN1 (RPG1; Guan et al, 2008; Sun et al, 2013), and NO PRIMEXINE AND PLASMA MEMBRANE UNDULATION (NPU; Chang et al, 2012). Disrupted primexine deposition leads to aberrant pollen wall patterning and ruptured pollen grains in these mutants

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