The rice thermo-sensitive genic male sterility gene tms9: pollen abortion and gene isolation

Abstract

The development of two-line hybrid rice has done great contribution to the food security. It is imperative to study the male sterility mechanism of rice photo-thermo sensitive genic male sterile (PTGMS) line which is the core component of two-line hybrid rice. Zhu1S is a rice thermo-sensitive genic male sterile line used frequently as female parent in two-line hybrid seed production. A cytological examination of the development of the Zhu1S anther wall and the microspores showed that tms9 encoded male sterility is caused by the failure of the tapetum to degenerate normally, thereby starving the microspores and finally leading to pollen abortion. A fine-scale genetic map based on a large F2 population allowed tms9 to be located within a 30.2 Kb segment of chromosome 2 harboring seven open reading frames. A comparison between Zhu1S under sterile temperature condition (high temperature, male sterile) and fertile temperature condition (low temperature, fertile) showed that only one of the seven genes, LOC_Os02g12290, was differentially transcribed, with its transcript abundance being much lower under the sterile temperature growing condition. LOC_Os02g12290 encodes a nuclear ribonuclease Z. Re-sequencing demonstrated that the Zhu1S LOC_Os02g12290 allele differed from that present in non tms9 carrier alleles by two contiguous nucleotides in the first exon, inducing a truncated mRNA.