Genome-wide gene expression profiling of rice stigma

In angiosperms, stigma provides initial nutrients and guidance cues for pollen grain germination and tube growth. However, little is known about genes that regulate these processes in rice. Here we generate rice stigma-specific gene expression profiles through comparing genome-wide expression patterns of hand dissected unpollinated stigma at anthesis with seven tissues including seedling shoot, seedling root, mature anther, ovary at anthesis, seeds of five days after pollination, 10-day-old embryo, 10-day-old endosperm as well as suspension cultured cells by using 57K Affymetrix rice whole genome array. In total, we identified 665 probe sets (550 genes) to be expressed specifically or predominantly in the stigma papillar cells of rice. Real-Time quantitative RT-PCR analysis of 34 selected genes confirmed their stigma-specific expression. The expression of five selected genes was further validated by RNA in situ hybridization. Gene annotation shows that several auxin-signaling components, transporters and stress-related genes are significantly overrepresented in the rice stigma gene set. We also found that genes involved in cell wall metabolism and cellular communication appear to be conserved in the stigma between rice and Arabidopsis. Our results indicate that the stigmas appear to have conserved and novel molecular functions between rice and Arabidopsis.

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Li M, Xu W, Yang W, Kong Z, Xue Y