Genetic, genomic, and proteomic studies of male-fertility restoration in onion.

摘要

Production of hybrid-onion seed is primarily dependent on the cytoplasmic-genic male sterility system discovered by Henry Jones. In this system, male sterility is conditioned by a male-sterile (S) cytoplasmic factor and the homozygous recessive genotype at the nuclear male-fertility-restoration (Ms) locus. The most effective way of seed propagating male-sterile lines (S msms) is by using a fertile maintainer line as the pollen donor, whose genotype must be N msms. The purpose of this research was to study the male-fertility restoration with the goal to identify markers that allow an early scoring of the genotype.;The first project was genetic analysis of male-fertility-restoration comparing testcross families, one in which all plants were derived from N MsMs plants, and a second family that segregated at Ms (N msms, N Msms, or N MsMs). Results show that the dominant Ms allele has incomplete penetrance, which makes it difficult to confidently score the testcross families and requires repetition across years and environments to be more certain about the genotype.;The rest of my research uses different approaches to try and identify the Ms locus. The first approach was to analyze expressed sequence tags of onion to identify pentatricopeptide (PPR) genes. Most of the cloned restorer-of-fertility genes belong to the PPR family of proteins. This candidate gene approach revealed PPR gene family structure in onion which was different from Arabidopsis or rice. However, no association was found between PPRs and Ms.;Suppression subtractive hybridization (SSH) was used to enrich for differentially expressed RNA between male-fertility-restored and male-sterile flowers. Three PPR genes were identified but no polymorphism was found. However, other genes from the SSH library might be of interest to pursue in the future.;A proteomics study was conducted to identify differentially accumulating proteins in male-fertility-restored and male-sterile flowers. The purification technique enriched for mitochondrial proteins which were separated through 2D gels. Three proteins showed differential accumulation, but no association with male-fertility-restoration was found.