MIR166a affects the germination of somatic embryos in Larix leptolepis by modulating IAA biosynthesis and signaling genes

作   者：李哲馨，张立峰，李万峰，齐力旺，韩素英
期刊名称：Journal of Plant Growth Regulation
影响因子：2.073
卷 期 号：36（4）
页     码：889-96
关键词：MiR166a，HD-ZIP III，Larix leptolepis，Somatic embryo，Germination，IAA 
论文摘要：
The somatic embryogenic regeneration system is an ideal model system to study the regulation of early
developmental processes and morphogenesis in gymnosperms. We have previously generated five larch (Larix
leptolepis) LaMIR166a overexpression cell lines. The germination rates of mature somatic embryos in transgenic
and wild-type (WT) lines were calculated and the results showed that overexpression of the miR166a precursor
(LaMIR166a) markedly enhanced germination, especially in the a-3, a-4, and a-5 lines. The relative expression of
LaMIR166a and miR166a in the LaMIR166a overexpression lines was higher than in the WT control line during
the germination process, whereas the expression levels of LaHDZ31–34 increased markedly throughout germination,
potentially as a result of feedback regulation of miR166. The effect of miR166a on auxin biosynthesis and signaling
genes was also studied. During germination, mRNA levels of Nitrilase (LaNIT), Auxin response factor1 (LaARF1),
and LaARF2 were markedly higher in LaMIR166a overexpressing lines. These results indicated that indole-3-acetic
acid (IAA) synthesis is required for germination in L. leptolepis. Further exogenous application of IAA at different
concentrations showed that 2 mg L−1 IAA clearly promoted germination, resulting in a 56% germination rate for L.
leptolepis somatic embryos. This shows that IAA plays a vital role in controlling the germination ability of someatic
embryos in L. leptolepis. Our results suggest that miR166a and LaHDZ31–34 have important roles in auxin biosynthesis
and signaling during the germination of somatic embryos in L. leptolepis.