DEP1 gene in wheat species with normal, compactoid and compact spikes

In rice, a variant of DEP1 gene results in erect panicle architecture, well-developed vascular bundles, an increase in the number of grains per panicle and a consequent increase in the grain yield. Interestingly, DEP1 homologs are present in the other cereals including species of wheat and barley (Hordeum vulgare), even though they do not produce panicles but spikes. In barley, HvDEP1 alleles do not differ between strains of various ear types and geographic origins, while in at least three OsDEP1 variants have been described.

In this work, we have studied the DEP1 gene from eight accessions which belong to four wheat species, T. monococcum, T. durum, T. compactum, and T. spelta, with either compact, compactoid or normal spike phenotypes. The nucleotide sequences of the 5th exon of DEP1 were determined for all eight accessions. Obtained sequences were species specific. Despite the interspecies diversity, all wheat sequences encoded polypeptides of the same size, similarly to the 5th exons of the DEP1 homologs in T. aestivum, T. urartu, and H. vulgare. For further study, the full-length sequences of the DEP1 gene for all four species were studied. The full-length DEP1 genomic copies were isolated from the genomic sequences of T. aestivum, T. urartu, and Aegilops tauschii. The genome of tetraploid wheat T. durum contains two variants of the DEP1 originating from A and B genomes. In the hexaploid wheats T. aestivum, T. compactum, and T. spelta, three variants of this gene originating from A, B, and D genomes were detected. DEP1 genes of the diploid wheats T. monococcum and T. urartu differ. It seems that a precursor of the DEP1 gene in T. monococcum originates from the wild progenitor T. boeoticum.

No DEP1-related differences of nucleotide sequences between the compact (or compactoid) and normal spike phenotypes in the tested wheat species were detected. Therefore, DEP1 gene does not directly participate in the control of the spike architecture in wheats.