Transcriptome sequencing to reveal the genetic regulation of leaf margin variation at early stage in birch

Lobe, a visual description of leaf morphology, is present in Betula pendula ‘Dalecarlica’. Although works involving leaf dehiscence have been conducted, knowledge on the genetic regulation of leaf morphology diversity at early stage remains largely elusive. Here, based on the extent of leaf margin variability, trees of B. pendula ‘Dalecarlica’ were categorized into A, B, and C. Plant materials of the apical buds from B. pendula ‘Dalecarlica’ (ASAM, BSAM, and CSAM) and B. pendula (OSAM), and young leaves from B. pendula ‘Dalecarlica’ (AYL and BYL) and B. pendula (OYL) were sampled for transcriptome sequencing. Compared with OSAM, there were 81, 6, and 17 genes in ASAM, BSAM, and CSAM. The expression of 204 genes was altered in OYL relative to OSAM. Meanwhile, the transcripts of 182 genes were changed in BYL relative to BSAM. In contrast to OYL, 337 genes and 47 genes were differentially expressed in AYL and BYL, respectively. Moreover, 91 genes with transcript changes were detected in BYL, as compared to AYL. The differentially expressed genes were annotated as having roles in antioxidant defense, cell division, and auxin synthesis at the apical bud stage. During the transition development from the apical buds to young leaves, genes showed homology with important enzymes of cell division, auxin signaling, and photosynthesis. At young leaf stage, genes were mainly involved in cell division, auxin signaling, and photosynthesis. Overall, the genes identified in our transcriptome profiles played potential roles in producing leaf splitting. This study sheds light on the genetic regulation of incised leaves at early stage in birch, which can serve as references for guiding the genetic manipulation in sculpturing leaf organ boundary.