Molecular Genetic Characteristics of Different Scenarios of Xylogenesis on the Example of Two Forms of Silver Birch Differing in the Ratio of Structural Elements in the Xylem.

Natalia A Galibina,Olga V Chirva,Diana S Ivanova,Ludmila I Semenova,Kseniya M Nikerova,Ludmila L Novitskaya,Aleksandra A Serkova,Tatiana V Tarelkina,Yulia L Moshchenskaya

doi:10.3390/plants10081593

Natalia A Galibina, Olga V Chirva + Show 7 more

Open Access

https://doi.org/10.3390/plants10081593

Copy DOI

Abstract

Silver birch (Betula pendula Roth) is an economically important species in Northern Europe. The current research focused on the molecular background of different xylogenesis scenarios in the birch trunks. The study objects were two forms of silver birch, silver birch trees, and Karelian birch trees; the latter form is characterized by the formation of two types of wood, non-figured (straight-grained) and figured, respectively, while it is currently not clear which factors cause this difference. We identified VND/NST/SND genes that regulate secondary cell wall biosynthesis in the birch genome and revealed differences in their expression in association with the formation of xylem with different ratios of structural elements. High expression levels of BpVND7 accompanied differentiation of the type of xylem which is characteristic of the species. At the same time, the appearance of figured wood was accompanied by the low expression levels of the VND genes and increased levels of expression of NST and SND genes. We identified BpARF5 as a crucial regulator of auxin-dependent vascular patterning and its direct target—BpHB8. A decrease in the BpARF5 level expression in differentiating xylem was a specific characteristic of both Karelian birch with figured and non-figured wood. Decreased BpARF5 level expression in non-figured trees accompanied by decreased BpHB8 and VND/NST/SND expression levels compared to figured Karelian birch trees. According to the results obtained, we suggested silver birch forms differing in wood anatomy as valuable objects in studying the regulation of xylogenesis.

Highlights

The xylem of woody plants is characterized by a wide range of its structural elements—vessels, fibrous tracheids, fibers, and radial and axial parenchyma cells
We studied the anatomical features of mature xylem of the sampled trees; carried out identification and research of the genes encoding NAC-domain transcription factors (VND, NST, and SND) that regulate secondary cell wall synthesis, development, and differentiation of xylem cells; transcription factor BpHB8 that promotes xylem production from the cambial cells, as well as auxin-dependent transcription factor BpARF5
We found that a high level of BpVND7 expression was confined to the differentiating xylem stage in 14-year-old birch plants, including xylem cells enlargement, secondary cell wall formation, and programmed cell death (PCD) of vessels and fibrous tracheids

Summary

Introduction

The xylem of woody plants is characterized by a wide range of its structural elements—vessels (water conduction function), fibrous tracheids (mechanical function as the main one and water conduction function), fibers (mechanical function), and radial and axial parenchyma cells (transport function and nutrient storage function). The xylem of woody plants is characterized by a wide range of its structural elements—. The whole variety of xylem structural elements originates from the stem cells of the lateral meristem called cambium. The differentiation stages of cambial derivatives into xylem elements include cell enlargement, the formation of a secondary cell wall (SCW), and in the case of fibers and vessels—programmed cell death (PCD) and autolysis of the cell content. Unlike poorly differentiated parenchyma cells, fibers and vessels are dead cells that consist only of cell walls. Cell walls in woody plants account for up to 90% of the dry weight. Compared to the thin primary cell walls (PCW), SCW are much thicker and account for most cellulosic biomass that serves as a renewable resource for biofuel production [1,2].

Objectives

Methods

Results

Discussion

Conclusion