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.
Highlights
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
A system that has been used for production of hybrids in many crop plants including maize, rice and sorghum is based on cytoplasmic male sterility (CMS), a mitochondrially-encoded trait[15,16,17], coupled with one or more nuclear Restorer-of-fertility (Rf) genes able to suppress CMS in F1 plants[14]
Based on studies in other plant species, it is known that Rf proteins are encoded in the nucleus and post-translationally imported to mitochondria, where they generally prevent the accumulation of gene products from CMS-specific open reading frames (ORFs)[17,19,20]
Summary
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. A system that has been used for production of hybrids in many crop plants including maize, rice and sorghum is based on cytoplasmic male sterility (CMS), a mitochondrially-encoded trait[15,16,17], coupled with one or more nuclear Restorer-of-fertility (Rf) genes able to suppress CMS in F1 plants[14]. This breeding system exploits the genes controlling gynodioecy in natural populations of many flowering plants. Both proteins bind to and induce cleavage of transcripts of a previously unrecognised mitochondrial gene (orf279) with no impact on the processing of orf[256], the gene previously thought to cause male sterility in wheat
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