Received February 21, 2008
Accepted April 16, 2008
RUPTURED POLLEN GRAIN 1 (RPG1), a Member of MtN3 /Saliva Gene Family, is Crucial for Exine Pattern Formation and Cell Integrity of Microspores in Arabidopsis thaliana
Yue-Feng Guan , Xue-Yong Huang , Jun Zhu , Ju-Fang Gao , Hong-Xia Zhang , and Zhong-Nan Yang *
National Key Laboratory of Plant Molecular Genetics, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, 300 Fenglin Road, Shanghai 200032, China; College of Life and Environment Sciences, Shanghai Normal University, 100 Guilin Road, Shanghai 200234, China
* Corresponding author; email: znyang{at}shnu.edu.cn.
During microsporogenesis, the microsporocyte (or microspore) plasma membrane plays multiple roles in pollen wall development, including callose secretion, primexine deposition, and exine pattern determination. However, plasma membrane proteins that participate in these processes are still not well known. Here, we report that a new gene, Ruptured Pollen Grain 1 (RPG1), encodes a plasma membrane protein and is required for exine pattern formation of microspores in Arabidopsis thaliana. The rpg1 mutant exhibits severely reduced male fertility with an otherwise normal phenotype, which is largely due to the post-meiotic abortion of microspores. Scanning Electron Microscopy (SEM) examination showed that exine pattern formation in the mutant is impaired, as sporopollenin is randomly deposited on the pollen surface. Transmission Electron Microscopy (TEM) examination further revealed that the primexine formation of mutant microspores is aberrant at the tetrad stage, which leads to defective sporopollenin deposition on microspores and the locule wall. In addition, microspore rupture and cytoplasmic leakage were evident in the rpg1 mutant, which indicates impaired cell integrity of the mutant microspores. RPG1 encodes an MtN3/saliva family protein that is integral to the plasma membrane. In situ hybridization analysis revealed that RPG1 is strongly expressed in microsporocyte (or microspores) and tapetum during male meiosis. The possible role of RPG1 in microsporogenesis is discussed.
