Effects of the protein GCP4 on gametophyte development in Arabidopsis thaliana.

γ-Tubulin complex protein 4 (GCP4, encoded by AT3G53760) participates in microtubule (MT) nucleation in Arabidopsis thaliana, affecting the MT nucleation angles in cortical MTs, and the formation of the spindle and phragmoplasts during mitosis. Here, we report that GCP4 plays a critical role in gametophyte development. The results indicate that the gcp4 mutant caused by T-DNA insertion may express an aberrant gene product interfering with normal GCP4 expression, ultimately leading to the formation of desiccated ovules and aborted seeds. An analysis of transmission efficiency (TE) indicated that female gametophytes were more impaired in development than male gametophytes, and so observation and analysis of gametophyte defects were conducted. Complementation lines obtained by the native promoter and GCP4-coded CDS gene sequence fused with GFP reduced the numbers of lethal phenotypes of the gcp4 mutant. The localization of GCP4 in the gametophyte was detected in cytoplasm around nuclei and in vicinity of plasma membrane of pollen grains, and also detected in full cytoplasm and around the nuclei of ovules in complementation line. Thus, it was established that GCP4 influences the functionality of gametophytes during gametophyte development.