Disruption of Long-Distance Transport Leads to Changes in Gene Expression Profiles of Sugar Transporters in Silver Birch

Karelian birch is a form of silver birch that is characterized by a violation of the ratio and spatial orientation of the structural elements of the trunk conductive tissues, resulting in the formation of typical figured wood. Karelian birch trees differ greatly in the degree of manifestation of abnormalities, and within the trunk of one tree there can be wood with normal and abnormal structure. The objects of study were 16-year-old common silver birch and Karelian birch trees with abnormal wood. We studied the expression profiles of genes encoding sucrose transporters to identify the role of apoplastic sucrose transport in the formation of trunk tissues in figure wood Karelian birch trees. For analysis, we selected figured and non-figured trunk section of the Karelian birch trees. We showed a sharp decrease in phloem conductivity in Karelian birch plants (2.3 times) compared to common silver birch. In addition to the inhibition of long-distance transport in Karelian birch trees, a disruption of the sucrose concentration gradient between the phloem and xylem was also observed, which probably contributes to the disruption of the symplastic radial transport of sugars to the developing wood. Changes in the symplastic transport system in Karelian birch led to an increased role of apoplastic transport, which was expressed in an increase in the gene expression of the SUT and SWEET gene families, encoding sucrose transporters that carry out transmembrane exchange of sucrose between cells and the apoplastic space.