Pervasive interactions of Sa and Sb loci cause high pollen sterility and abrupt changes in gene expression during meiosis that could be overcome by double neutral genes in autotetraploid rice

Jinwen Wu,Qinglei Dong,Xiaosong Xu,Jirui Li,Xiangdong Liu,Minyi Chen,Muhammad Qasim Shahid,Lin Chen

doi:10.1186/s12284-017-0188-8

Abstract

BackgroundIntersubspecific autotetraploid rice hybrids possess high hybrid vigor; however, low pollen fertility is a critical hindrance in its commercial utilization. Our previous study demonstrated that polyploidy could increase the multi-loci interaction and cause high pollen abortion in autotetraploid rice hybrids. However, there is little known about the critical role of pollen sterility locus or loci in the intersubspecific hybrids. We developed autotetraploid rice hybrids harboring heterozygous genotypes (SiSiSjSj) at different pollen sterility loci by using the near isogenic lines of Taichung65-4×. Moreover, autotetraploid lines carrying double neutral genes, San and Sbn, were used to assess their effect on fertility restoration.ResultsCytological studies showed that the deleterious genetic interactions at Sa and Sb pollen sterility loci resulted in higher pollen sterility (76.83%) and abnormal chromosome behavior (24.59%) at metaphase I of meiosis in autotetraploid rice hybrids. Transcriptome analysis revealed 1092 differentially expressed genes (DEG) in a hybrid with the pervasive interactions at Sa and Sb pollen sterility loci, and most of the genes (about 83%) exhibited down regulation. Of the DEG, 60 were associated with transcription regulation and 18 genes were annotated as meiosis-related genes. Analysis on the hybrids developed by using autotetraploid rice harboring double neutral genes, San and Sbn, revealed normal pollen fertility, and transcriptome analysis showed non-significant difference in number of DEG among different hybrids.ConclusionsOur finding revealed that pervasive interactions at Sa and Sb pollen sterility loci cause high sterility in the autotetraploid hybrids that lead to the down-regulation of important meiosis-related genes and transcription regulation factors. Moreover, we also found that the hybrids sterility could be overcome by double neutral genes, San and Sbn, in autotetraploid rice hybrids. The present study provided a strong evidence for the utilization of heterosis in autotetraploid rice hybrids.

Highlights

Intersubspecific autotetraploid rice hybrids possess high hybrid vigor; low pollen fertility is a critical hindrance in its commercial utilization
Our previous transcriptome analysis revealed significant variations between autotetraploid and diploid rice hybrids harboring triple pollen sterility loci (SaSbSc) interactions, and we found that polyploidy enhanced F1 pollen sterility loci interactions that increase meiosis abnormalities and pollen sterility in autotetraploid rice (Wu et al 2015)
Pervasive interactions at Sa and Sb pollen sterility loci cause low pollen fertility and abortion of male meiocytes in autotetraploid rice hybrids To explore the effect of pollen sterility loci caused by the genetic interactions of Sa, Sb and Sc pollen sterility loci, the genotypes of autotetraploid rice hybrids were screened by closely linked molecular makers (Additional files 1 and 2: Figures S1 and S2)

Summary

Introduction

Intersubspecific autotetraploid rice hybrids possess high hybrid vigor; low pollen fertility is a critical hindrance in its commercial utilization. Our previous study demonstrated that polyploidy could increase the multi-loci interaction and cause high pollen abortion in autotetraploid rice hybrids. Intersubspecific autotetraploid rice hybrids showed significant heterozygosity and hybrid vigor compared to diploid rice hybrids, low seed set is one of the critical hindrances in its utilization (Shahid et al 2013; Wu et al 2013). Abnormal chromosome behavior during meiosis was the primary cause of pollen sterility in autotetraploid rice hybrids (Luan et al 2007; He et al 2011; Wu et al 2015). Polyploidy enhanced multi-F1 pollen sterility loci interactions that increased meiosis abnormalities and lead to high pollen sterility in autotetraploid rice hybrids (Wu et al 2015)

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