BpIAA10 interacts with BpIAA7 and BpARF19 to regulate the growth and differentiation of embryonic leaves in birch (Betula platyphylla)

Abstract The Auxin/Indole acetic acid (Aux/IAA) family is an important class of auxin-response genes involved in leaf development in Arabidopsis. However, the biological function of these genes remains unclear in perennial wood plants. In this study, we identified an Aux/IAA10 gene (BpIAA10) from birch (Betula platyphylla) that is associated with growth of embryonic leaves. The result was confirmed by gain- and loss-of-function analysis of BpIAA10. Transgenic birch overexpressing (OE) and repressing (RE) BpIAA10 exhibited significantly increased numbers of embryonic leaves and stipules than non-transgenic lines (NT). The IAA concentration was increased by 3.50 and 3.61-fold in OE and RE lines than NT, respectively. Yeast two-hybrid and bimolecular fluorescence complementation (BiFC) analysis revealed that BpIAA10 specifically interacts with BpIAA7 and BpARF19 during leaf development. In addition, we found both overexpression and repression of BpIAA10 affected the expression of auxin biosynthesis and metabolism genes, auxin response genes, and leaf development genes. All these results indicated that BpIAA10 is involved in the differentiation and growth of embryonic leaves by specific interactions and complex regulation with components of the birch auxin response pathway. Our findings provide insights into leaf growth and differentiation in perennial trees.