In Silico Analysis of Regulatory cis-Elements in the Promoters of Genes Encoding Apoplastic Invertase and Sucrose Synthase in Silver Birch

This work is a continuation of studies on the role of sucrose in the formation of figured wood of Karelian birch (Betula pendula Roth var. carelica (Merckl. Hämet-Ahti). It was previously established that this type of xylogenesis is accompanied by significant changes in activity of sucrose-metabolizing enzymes, sucrose synthase and invertase, in the birch trunk’s tissues. The results of molecular genetic analysis indicate that the activity of these enzymes is regulated mainly at the level of transcription of the genes encoding them (SUS and CWInv). The genes encoding sucrose synthase and cell-wall invertase in the silver birch genome were identified. In silico analysis of the regulatory cis-elements present in the 2-kb promoter region of these genes revealed a number of motifs involved in the regulation of their expression. The largest (in terms of both the number of individual elements and their occurrence) was the group of elements associated with the influence of abiotic factors, mainly light and drought. A number of tissue-specific motifs, the function of which is associated with gene expression in conducting tissues, were identified. Analysis of hormone-dependent elements showed that the formation of figured wood of Karelian birch, which occurs against the background of high apoplastic invertase activity, is obviously not associated with the activation of CWInv genes by a high level of auxin. In the studied promoter sequences, various elements indicating the direct effect of sugar signaling were found. Two most likely candidates for involvement in the regulation of carbohydrate metabolism in the birch trunk tissues—transcription factors (TF) DOF5.6 (HCA2) and DOF5.8—were identified. The identification and functional characteristics of the DOF family TFs of silver birch are of interest from the point of view of the regulation of alternative scenarios of xylogenesis.