[Cloning of tae-MIR156 precursor gene and sequence polymorphisms of tae-miR156 targeted TaSPL17].

Squamosa-promoter binding protein (SBP)-box genes, encoding plant-specific transcription factors, play an important role in plant development. Some members of the SBP-box gene family are regulated by miR156. In this study, we cloned the tae-MIR156 precursor gene, which could form a stem loop after its transcription. Sequence analysis showed that TaSPL3 and TaSPL17 had putative targets of tae-miR156 among the ten wheat SBP-box genes. The diploid donor species of hexaploid common wheat (Triticum aestivum, genome AABBDD), i.e., Triticum urartu (AA) UR209 and Aegilops speltoides Y2001 (SS, closely related to BB) possessed more than one copy of SPL17 (SPL17-A1, SPL17-A2 and SPL17-A3 from Triticum urartu; SPL17-B1, SPL17-B2 and SPL17-B3 from Aegilops speltoides), while Aegilops tauschii (DD) Ae38 only possessed one (SPL17-D). The identities between nucleotide sequences of SPL17-A2 and SPL17-B2, SPL17-A3 and SPL17-B3 or SPL17-D were higher than 99%. They were highly similar with the sequence of TaSPL17 in common wheat cultivars Chinese Spring, Hengguan 35 and Shuangfengshou. These genes might originate from a common ancestor and were highly conserved in the process of evolution. The target site of tae-miR156 in TaSPL17 was also highly conserved in two subgroups consisted of accessions with diverse spike number per plant and genetic background.