Sex‐independent transmission ratio distortion system responsible for reproductive barriers between Asian and African rice species

Abstract

Summary• A sex-independent transmission ratio distortion (siTRD) system detected in the interspecific cross in rice was analyzed in order to understand its significance in reproductive barriers. The S 1 gene, derived from African rice Oryza glaberrima, induced preferential abortion of both male and female gametes possessing its allelic alternative ( ), from Asian rice O. sativa, only in the heterozygote.• The siTRD was characterized by resolving it into mTRD and fTRD occurring through male and female gametes, respectively, cytological analysis of gametophyte development, and mapping of the S 1 locus using near-isogenic lines. The allelic distribution of the S 1 locus in Asian and African rice species complexes was also analyzed.• The siTRD system involved at least two components affecting male and female gametogeneses, respectively, including a modifier(s) that enhances fTRD. The chromosomal location of the major component causing the mTRD was delimited within an approx. 40 kb region. The S 1 locus induced hybrid sterility in any pairwise combination between Asian and African rice species complexes.• The allelic state of the S 1 locus has diverged between Asian and African rice species complexes, suggesting that the TRD system has a significant role in the reproductive barriers in rice.

Identification of QTLs for Agronomic Characteristics in An Upland New Rice for Africa (NERICA) Variety

“…Our findings that there were no QTLs for SF and no markers showing significant segregation ratio distortion, except in the chromosomal region near S1, suggest that S1 is the main genetic factor causing hybrid sterility in crosses between NERICA10 and WAB56-104. These findings, together with the information revealed by Koide et al (2008) on the position of S1, will facilitate the development of DNA markers for selecting out hybrid sterility genes in NERICA varieties.…”

“…The S1 allele, which is derived from O. glaberrima, causes preferential dysfunction of male and female gametes carrying its opposite allele (S1 a ) derived from O. sativa in heterozygotes (S1/S1 a ). Thus, segregation ratio distortion is observed in later generations of heterozygotes (Sano 1990, Koide et al 2008, Garavito et al 2010). In our study, at marker RM19387 in this QTL region, heterozygotes had significantly lower seed fertility (60.4%) than homozygotes for the parental allele (81.4%).…”

“…Our results showed the presence of a QTL for SF on the short arm of chromosome 6. In this chromosomal region, the hybrid sterility gene S1, which causes both pollen and seed sterility in the heterozygote has been identified in a cross between O. sativa and O. glaberrima (Sano 1990, Koide et al 2008, Garavito et al 2010). The S1 allele, which is derived from O. glaberrima, causes preferential dysfunction of male and female gametes carrying its opposite allele (S1 a ) derived from O. sativa in heterozygotes (S1/S1 a ).…”

Complex genetic nature of sex-independent transmission ratio distortion in Asian rice species: the involvement of unlinked modifiers and sex-specific mechanisms

“…Among them, TRD occurring in either the male (mTRD) or female (fTRD) gametes has been frequently reported and some of the genes causing sex-specific TRD have been cloned Long et al, 2008). On the other hand, there are few reports on sex-independent TRD (siTRD), which results from preferential transmission of both male and female gametes carrying one of the two alleles in the heterozygote (Rick, 1966;Koide et al, 2008c). Little is known about the genetic basis and evolutionary history of siTRD, although siTRD exerts the strongest effect on segregation distortion among these types of TRD.…”

Hybrid Sterility in Rice (Oryza sativa L.) Involves the Tetratricopeptide Repeat Domain Containing Protein

“…According to the classical Dobzhansky-Muller model, postzygotic isolation results from a deleterious interaction between functionally diverged genes from the hybridizing species (Dobzhansky 1937;Ting et al 1998;Barbash et al 2003;Presgraves et al 2003;Brideau et al 2006;Bayes and Malik 2009;Ferree and Barbash 2009;Phadnis and Orr 2009;Tang and Presgraves 2009;White et al 2011). Genes for hybrid sterility, a common pattern of postzygotic isolation, have been reported in several organisms, including fungi, animals, and plants (Brideau et al 2006;Lee et al 2008;Bikard et al 2009;De Vienne et al 2009).Major progress has been made in rice and the interspecific and intersubspecific hybrid sterilities are perhaps the best known examples (Chen et al 2008;Long et al 2008 Wan and Ikehashi 1995;Zhu et al 2005;Li et al 2007;Zhao et al 2007;Chen et al 2008Chen et al , 2012Yang et al 2012), pollen sterility Jing et al 2007;Kubo et al 2008Kubo et al , 2011Long et al 2008;Zhang et al 2011;Zhao et al 2011), and both in a few cases (Koide et al 2008(Koide et al , 2012. The S7 locus was first identified causing hybrid sterility between an Aus variety "Ingra" and some javanica varieties by Ikehashi and Araki (1987).…”