New Insights Into the Nature of Interspecific Hybrid Sterility in Rice.

Jing Li,Jiawu Zhou,Yu Zhang,Ying Yang,Qiuhong Pu,Dayun Tao

doi:10.3389/fpls.2020.555572

Jing Li, Jiawu Zhou + Show 4 more

Open Access

https://doi.org/10.3389/fpls.2020.555572

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Abstract

Interspecific and intraspecific hybrid sterility is a typical and common phenomenon of postzygotic reproductive barrier in rice. This is an indicator of speciation involved in the formation of new species or subspecies, and it significantly hampers the utilization of favorable genes from distant parents for rice improvement. The Oryza genus includes eight species with the same AA genome and is a model plant for studying the nature of hybrid sterility and its relationship with speciation. Hybrid sterility in rice is mostly controlled by nuclear genes, with more than 50 sterility loci genetically identified to date, of which 10 hybrid sterility loci or pairs were cloned and characterized at the molecular level. Comparing the mapping results for all sterility loci reported indicated that some of these loci from different species should be allelic to each other. Further research revealed that interactions between the multiple alleles at the hybrid sterility locus caused various genetic effect. One hypothesis for this important phenomenon is that the hybrid sterility loci are orthologous loci, which existed in ancient ancestors of rice. When one or more ancestors drifted to different continents, genetic divergence occurred because of adaptation, selection, and isolation among them such that various alleles from orthologous loci emerged over evolutionary time; hence, interspecific hybrid sterility would be mainly controlled by a few orthologous loci with different alleles. This hypothesis was tested and supported by the molecular characterization of hybrid sterility loci from S1, S5, Sa, qHMS7, and S27. From this, we may further deduce that both allelic and non-allelic interactions among different loci are the major genetic basis for the interspecific hybrid sterility between O. sativa and its AA genome relatives, and the same is true for intraspecific hybrid sterility in O. sativa. Therefore, it is necessary to raise the near-isogenic lines with various alleles/haplotypes and pyramided different alleles/haplotypes from sterile loci in the same genetic background aiming to study allelic and non-allelic interaction among different hybrid sterility loci in the AA genome species. Furthermore, the pyramiding lines ought to be used as bridge parents to overcome hybrid sterility for rice breeding purposes.

Highlights

Reproductive barriers are very common and important phenomena in biology, being widely observed in animal and plant populations
Based upon published reports of more than 50 sterility loci genetically identified, and 10 hybrid sterility loci or pairs cloned and characterized at the molecular level, this review examines the links between the evolutionary relationship of the Oryza genus and hybrid sterility, the genetic models of hybrid sterility, the allelic variation of orthologous loci for hybrid sterility, the nonallelic interactions for hybrid sterility, and strategies for overcoming hybrid sterility in rice improvement
The pollen killer locus S55(t)/qHMS7, from O. meridionalis, has a map position similar to that of S21 identified from O. rufipogon, O. glaberrima, and S23(t) identified from O. glumaepatula (Doi et al, 1999; Sobrizal et al, 2000b; Miyazaki et al, 2007; Li et al, 2018b; Yu et al, 2018). This congruence pointed to a major pollen sterility locus on the long arm of chromosome 7 that is capable of inducing sterility in the hybridization combinations arising from O. sativa crossed with O. glaberrima, O. rufipogon, O. glumaepatula, and O. meridionalis, respectively, whose sequence analysis was based on the cloning of S23 and qHMS7 (Yu et al, 2018; Fang et al, 2019)

Summary

Introduction

Reproductive barriers are very common and important phenomena in biology, being widely observed in animal and plant populations. The molecular evolution analysis of the S5 locus, one of the important female sterility loci in indica-japonica hybrids, revealed that indica and japonica subspecies of the Asian cultivated rice O. sativa were domesticated independently from wild species (Du et al, 2011).

Results

Conclusion