The genetic basis of cytoplasmic male sterility and fertility restoration in wheat

Abstract

Hybrid wheat varieties give higher yields than conventional lines but are difficult to produce due to a lack of effective control of male fertility in breeding lines. One promising system involves the Rf1 and Rf3 genes that restore fertility of wheat plants carrying Triticum timopheevii-type cytoplasmic male sterility (T-CMS). Here, by genetic mapping and comparative sequence analyses, we identify Rf1 and Rf3 candidates that can restore normal pollen production in transgenic wheat plants carrying T-CMS. We show that Rf1 and Rf3 bind to the mitochondrial orf279 transcript and induce cleavage, preventing expression of the CMS trait. The identification of restorer genes in wheat is an important step towards the development of hybrid wheat varieties based on a CMS-Rf system. The characterisation of their mode of action brings insights into the molecular basis of CMS and fertility restoration in plants.

Identification of Rf Genes in Hexaploid Wheat (Triticumaestivum L.) by RNA-Seq and Paralog Analyses

“…However, one should consider the essential differences between both systems of sterility and, consequently, the differences in the expression of genes mediating fertility restoration. Furthermore, the mitochondrial gene orf279, which is important for the cms trait [47], is highly expressed in the early anthesis stage. Its transcript, which is targeted by the proteins encoded by at least two Rf genes (Rf1 and Rf3), is also produced at a relatively early microsporogenesis stage.…”

“…These proteins stabilize organellar transcripts and intron splicing [75][76][77]. A recent study by Melonek et al [47] proved that two PPR proteins (encoded by Rf1 and Rf3) target the mitochondrial orf279 transcript. The binding of these two proteins to this transcript leads to cleavage and prevents the expression of the cms trait.…”

“…Along with the availability of a wheat reference genome [81], molecular markers developed for decades by wheat researchers can now be physically mapped and compared with the positions of candidate DEGs or PAGs with defined expression patterns. To date, several types of molecular markers, including restriction fragment length polymorphism (RFLP), simple sequence repeat (SSR), SNP, kompetitive allele-specific PCR (KASP), and diversity arrays technology (DArT) markers, have been linked to the following seven Rf genes: Rf1 [46,47,82], Rf2 [50], Rf3 [39][40][41][42]47,49,82,83], Rf4 [41], Rf6 [35], Rf8 [36], and Rf9 [39]. The DNA sequences of all available genetic markers flanking the genes and QTLs related to fertility restoration were used to delimit target regions.…”

“…Another major dominant restorer gene, Rf9, was detected in the subtelomeric region of chromosome 6AS [39]. Melonek et al [47] recently identified Rf1 and Rf3 via genetic mapping, comparative sequence analyses, and functional studies. The proteins encoded by these two genes bind to the mitochondrial orf279 transcript of a newly identified mitochondrial gene and induce its cleavage, thereby blocking the expression of the cms trait.…”

Male Fertility Genes in Bread Wheat (Triticum aestivum L.) and Their Utilization for Hybrid Seed Production

“…Consequently, it is required to stack multiple Rf genes in a genotype-dependent combination to achieve complete fertility of F 1 hybrids. In the past, stacking and breeding of restorer genes has proved challenging, although with contemporary genomics and molecular breeding techniques it is now possible to precisely track Rf genes for breeding [79]. Another major limitation for utilizing a CMS for hybrid seed production is the requirement for A × B crossing for female parent seed increase (Figure 4).…”