期刊
ANNALS OF FOREST SCIENCE
卷 74, 期 1, 页码 -出版社
SPRINGER FRANCE
DOI: 10.1007/s13595-016-0613-y
关键词
Wood; Tree-ring; Cambium; Morphogen; Xylogenesis; Model
类别
资金
- French National Research Agency (ANR) as part of the 'Investissements d'Avenir' program (Lab of Excellence ARBRE) [ANR-11-LABX-0002-01]
Key message The emergence of the characteristic treering pattern during xylogenesis is commonly thought to be controlled by a gradient of morphogen (auxin, TDIF peptide...). We show that this hypothesis accounts for several developmental aspects of wood formation, but not for the final anatomical structure. Context Wood formation is a dynamic cellular process displaying three generic features: (i) meristematic cell proliferation is restricted to the small cambial zone, preventing exponential xylem radial growth along the growing season; (ii) developmental processes result in a stable zonation of the developing xylem; (iii) the resulting mature wood cells form the typical tree-ring structure made of early and late wood with a gradient of cell sizes, an important trait for wood functioning in trees and for lumber quality. The mechanisms producing these spatial-temporal patterns remain largely unknown. According to the often-cited morphogenetic-gradient hypothesis, a graded concentration profile of a signalling molecule (e. g. auxin, TDIF) controls xylogenesis by providing positional information to differentiating cells. Aims We assessed the predictions of the morphogeneticgradient theory. Methods We developed a computational model of wood formation implementing hypotheses on how a morphogen flows through the developing xylem and controls cell division and growth and we tested it against data produced by studies monitoring wood formation in conifers. Results We demonstrated that a morphogenetic gradient could indeed control xylem radial growth and woodforming tissue zonation. However, it failed to explain the pattern of final cell sizes observed in tree-rings. We discussed the features that candidate additional regulatory mechanisms should meet.
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