Expression Analysis of Key Auxin Biosynthesis, Transport, and Metabolism Genes of Betula pendula with Special Emphasis on Figured Wood Formation in Karelian Birch.

Tatiana V Tarelkina,Kseniya M Nikerova,Yulia L Moshchenskaya,Diana S Ivanova,Nadezhda N Nikolaeva,Ludmila L Novitskaya,Irina N Sofronova,Ludmila I Semenova,Natalia A Galibina

doi:10.3390/plants9111406

Tatiana V Tarelkina, Kseniya M Nikerova + Show 7 more

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https://doi.org/10.3390/plants9111406

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Abstract

Auxin status in woody plants is believed to be a critical factor for the quantity and quality of the wood formed. It has been previously demonstrated that figured wood formation in Karelian birch (Betula pendula Roth var. carelica (Merckl.) Hämet-Ahti) is associated with a reduced auxin level and elevated sugar content in the differentiating xylem, but the molecular mechanisms of the abnormal xylogenesis remained largely unclear. We have identified genes involved in auxin biosynthesis (Yucca), polar auxin transport (PIN) and the conjugation of auxin with amino acids (GH3) and UDP-glucose (UGT84B1) in the B. pendula genome, and analysed their expression in trunk tissues of trees differing in wood structure. Almost all the investigated genes were overexpressed in Karelian birch trunks. Although Yucca genes were overexpressed, trunk tissues in areas developing figured grain had traits of an auxin-deficient phenotype. Overexpression of GH3s and UGT84B1 appears to have a greater effect on figured wood formation. Analysis of promoters of the differentially expressed genes revealed a large number of binding sites with various transcription factors associated with auxin and sugar signalling. These data agree with the hypothesis that anomalous figured wood formation in Karelian birch may be associated with the sugar induction of auxin conjugation.

Highlights

The hormone auxin is involved in regulating virtually all morphogenetic processes in plant organisms, and its role in conducting tissues differentiation in tree trunks is well known [1,2,3,4,5,6,7,8].Auxin contribution to the regulation of morphogenetic processes largely depends on its concentration and distribution in plant organs and tissues
For promoters of Set 2 genes, we revealed 168 and 126 transcription factor binding sites (TFBS) were overrepresented compared to promoters in A. thaliana and P. trichocarpa, respectively
We have identified the key genes involved in auxin biosynthesis, transport and conjugation in the Betula pendula Roth genome and investigated their expression in trunk tissues and leaves of adult birch trees with different anatomical structure of the wood

Summary

Introduction

The hormone auxin is involved in regulating virtually all morphogenetic processes in plant organisms, and its role in conducting tissues differentiation in tree trunks is well known [1,2,3,4,5,6,7,8]. Auxin contribution to the regulation of morphogenetic processes largely depends on its concentration and distribution in plant organs and tissues. The level of free (physiologically active) auxin in cells and tissues is the result of an intricate crosstalk of processes for its transport and metabolism, which, in turn, includes hormone biosynthesis, degradation and conjugation [9,10,11]. The principal gene families involved in IAA (the main natural auxin form) homeostasis in tissues have been identified. Yucca family genes have been detected in many plants, including woody plants—Populus trichocarpa [12], Vitis vinifera [13], Prunus persica [14], Plants 2020, 9, 1406; doi:10.3390/plants9111406 www.mdpi.com/journal/plants

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