Expression of BpPIN is associated with IAA levels and the formation of lobed leaves in Betula pendula ‘Dalecartica’

Auxin polar transport genes PIN (PIN-FORMED) determine the concentration gradient of auxin in plants. To understand the relationship between the development of different tissues in Betula pendula ‘Dalecartica’, BpPIN gene expression and indole-3-acetic acid (IAA) content were analyzed using qRT-PCR, ELISA, and GUS staining. Gene expression of BpPIN genes and IAA levels in the leaves, buds, stems, xylem, and roots of B. pendula ‘Dalecartica’ and B. pendula as a control were measured. BpPIN1, BpPIN5 and BpPIN6 were upregulated during development in both species, suggesting a dominant role in the development of B. pendula ‘Dalecartica’ leaves. Moreover, BpPIN1 gene expression was positively associated with IAA levels during leaf, vein and petiole development in B. pendula ‘Dalecartica’ only. The correlation coefficient of the first three leaves was 0.69 (P = 0.04), while that of the first three petioles was 0.85 (P = 0.001). In addition, GUS staining of the pro-DR5::GUS transgenic line of cultivar was correlated with the results of BpPIN1 expression. Overall, these findings suggest that BpPIN1 is associated with the formation of lobed leaves in B. pendula ‘Dalecartica’.