Effect analysis of S5-interacting genes on rice hybrid sterility using nontransgenic gamete killer
Year: 2024
Type: article
Abstract: While hybrids between japonica and indica rice exhibit strong heterosis, they often suffer from hybrid sterility (HS). Hybrid fertility of the embryo sac is predominantly regulated by a three-gene system (comprising closely linked ORF3, ORF4 and ORF5) at rice S5 locus. The cooperation of ORF5+ and ORF4+ can sporophytically kill all embryo sacs, while ORF3+ can gametophytically protect the half embryo sac. We previously identified four S5-interacting genes (SIGs) using hybrid progeny (with spikelet fertility (SF) about 65%) between a transgenic line BLORF5+ (Balilla carrying transgenic ORF5+, SF< 5%) and a wide compatibility variety Dular (DL or D), and their effects on HS were analyzed using near isogenic lines (NILs), demonstrating DL allele as the fertility-enhancing allele for all SIGs. Homozygote and hemizygote of ORF5+ transgene had significantly different SF, which disturbed the phenotypic effects of SIGs. However, HS effects of SIGs under the endogenous (nontransgenic) gamete killer remained unknown. We formerly constructed a semisterile NIL S5-BL/NJ by introgressing S5 fragment of indica rice Nanjing11 (NJ or N) into the genome of japonica rice Balilla (BL or B). BL and NJ carry ORF3-ORF4+ORF5- and ORF3+ORF4-ORF5+ haplotypes respectively. The gamete-protecting effect of ORF3+ in NJ may confuse SF effect of the SIGs, so we knocked out ORF3+ of S5-NJ/NJ and crossed it with BL to get gamete-killing S5-BL/NJΔORF3+, which can kill all (KA) gametes (abbreviated as enS5KA). Compared with the exogenous S5 (exS5KA, i.e. BLORF5+ with ORF5+ transgene), the enS5KA conferred SIGs a more pronounced SF effect. The enS5KA,SIG-DDDD (SIGs carry homozygous DL alleles) genotype caused a SF of about 78%, while SF of exS5KA,SIG-DDDD was only about 62%. Moreover, all SIGs acted in a sporophytic manner without segregation distortion of genotype. Although enS5KA,SIG-DDDD plants had high SF, the ER stress still existed. The ovule section revealed that enS5KA,SIG-BBBB genotype (SIGs carry homozygous BL allele, with ER stress and SF< 5%) caused abnormal degradation of nucellar cells and functional megaspores. In contrast, enS5KA,SIG-DDDD genotype preserved most nucellar cells and functional megaspores. These results lay the foundation for further research on HS mechanism of S5 and SIGs and cloning of candidate genes.
Source: Plant Science
Language: English
Topic: Plant Reproductive Biology
Subfield: Molecular Biology
Domain: Life Sciences
SDG: Zero hunger
Open Access status: hybrid
Estimated APC paid: $3,650
OpenAlex ID: W4405364352