Cytological and Transcriptomic Analyses Reveal Important Roles of CLE19 in Pollen Exine Formation
First author:Shuangshuang Wang; Affiliations: Fudan University(复旦大学): Shanghai, China
Corresponding author:Fang Chang (常芳)
The CLAVATA3/ESR-RELATED (CLE) peptide signals are required for cell-cell communication in several plant growth and developmental processes. However, little is known regarding possible functions of the CLEs in the anther. Here, we show that a T-DNA insertional mutant, and dominant-negative (DN; 显性负性) and overexpression (OX) transgenic plants of the CLE19 gene exhibited significantly reduced anther size and pollen grain number, and abnormal pollen wall formation. Interestingly, the DN-CLE19 pollen grains showed a more extensively covered surface but CLE19-OX pollen exine exhibited clearly missing connections in the network and lacked separation between areas that normally form the lacunae (腔隙). With a combination of cell biological, genetic, and transcriptomic analyses on cle19, DN-CLE19, and CLE19-OX plants, we demonstrated that CLE19-OX plants produced highly vacuolated (有空泡的) and swollen (膨胀的) ams-like tapetal cells (绒毡层细胞), lacked lipidic tapetosomes (含油体) and elaioplasts (油粒体), and had abnormal pollen primexine (初生外壁) without obvious accumulation of sporopollenin (孢粉素) precursors. Moreover, CLE19 is important for the normal expression of > 1,000 genes, including transcription factor gene AMS, 280 AMS-downstream genes, and other genes involved in pollen coat (花粉外被) and pollen exine (花粉外壁) formation, lipid metabolism, pollen germination, and hormone metabolism. In addition, the DN-CLE19(+/+) ams(-/-) plants exhibited the ams anther phenotype and ams(+/-) partially suppressed the DN-CLE19 transgene-induced pollen exine defects. These findings demonstrate that the proper amount of CLE19 signal is essential for the normal expression of AMS and its downstream gene networks in the regulation of anther development and pollen exine formation.