Towards the positional cloning of Eps-Am1, an earliness per se gene, in Triticum monococcum L.

摘要

An earliness per se gene, designated Eps-A m1, was mapped on the long arm of chromosome 1AmL in a population derived from a cross between cultivated Triticum monococcum ssp. monococcum accession DV92 and wild Triticum monococcum ssp. aegilopoides accession G3116. Phenotypic experiments using BC6F2 near isogenic lines with critical recombination events in the Eps-Am1 region showed that in the lines carrying the late-flowering Eps-Am1-l alleles from DV92 the transition from the vegetative to the reproductive stages occurred later, the spike development period was longer, and the number of spikelets per spike was larger than in the lines carrying the early-flowering Eps-Am1-e alleles from G3116. A gene with a similar effect was found to be located on the distal 83% of chromosome 1AL of hexaploid wheat by using cytogenetic stocks for the homoeologous group 1 chromosomes. A high-density genetic map of the Eps-Am1 region was constructed in T. monococcum, and physical maps of the same region were developed in this species and also in Aegilops tauschii and Brachypodium distachyon. The Eps-Am1 region was found to encompass ∼300 kb corresponding to 0.06 cM flanked by genes CtE1 and Adk1. Three candidate genes for Eps-A m1 were identified: Fop1, a flavonoid 3'-hydroxylase; Mot1, a global transcriptional regulator; FtsH4, a peptidase. The protein products of these genes were compared between the DV92 and G3116 alleles. Whereas no amino acid polymorphisms were found for protein FtsH4, two and three amino acid substitutions were identified for proteins MOT1 and FOP1, respectively. The analysis of the transcription profiles of the three candidate genes in shoot apical regions revealed non-significant differences between the transcript levels of lines carrying either the early or late Eps-Am1 alleles. Based on the known function of related proteins, Mot1 is most likely the strongest candidate gene. Mutants mot1 were identified in tetraploid and hexaploid wheat using a TILLING approach, and they will be phenotypically evaluated to test if gene Mot1 is, in fact, Eps-A m1.