UPBEAT1-ROS-POD-PAL System under Different Xylogenesis Scenarios in Karelian Birch (Betula pendula Roth var. carelica (Mercl.) Hämet-Ahti)

Abstract

Background: We studied UPBEAT1 (UPB1) which regulated superoxide radical / hydrogen peroxide ratio together with peroxidase (POD) activity and PAL genes expression under different ways of apical meristem development during the xylem structural elements’ formation in unique woody plants B. pendula var. pendula with straight-grained wood and B. pendula var. carelica with figured wood. The differentiation process predominanced in straight-grained wood (B. pendula var. pendula) or proliferation – in the figured wood. The investigation was conducted in the radial row (cambial zone - differentiating xylem - mature xylem) during the active cambial growth period. Objective: The study aimed to study the xylogenesis processes occurring in the 16-year-old straight-grained silver birch (Betula pendula Roth) and Karelian birch (Betula pendula Roth var. carelica (Mercl.) Hämet-Ahti) with figured wood. Methods: Hydrogen peroxide and superoxide radical contents and peroxidase activity were determined spectrophotometrically. Gene expression for PAL family genes and the UPBEAT1 gene was assessed using qRT-PCR. Results: Principal component analysis has confirmed trees with straight-grained and figured wood to be different according to UPBEAT1-ROS-POD-PAL system functioning. Conclusion: The higher superoxide radical/hydrogen peroxide ratio in figured Karelian birch, along with UPBEAT1 transcription factor and PAL genes upregulation, distinguished it from straight-grained silver birch. This metabolic picture confirmed the shift of Karelian birch xylogenesis towards proliferation processes, accompanied by ROS and phenolic compounds’ flow and POD activity.