School of Landscape Architecture, Beijing University of Agriculture, Beijing 102206,China.
National Engineering Research Center of Tree Breeding and Ecological Restoration, College of Biological Sciences and Technology, Beijing Forestry University, Beijing 100083,China.
Plant Cell. 2023 Oct 30;35(11):4046-4065. doi: 10.1093/plcell/koad212.
Perennial trees must maintain stem growth throughout their entire lifespan to progressively increase in size as they age. The overarching question of the molecular mechanisms that govern stem perennial growth in trees remains largely unanswered. Here we deciphered the genetic architecture that underlies perennial growth trajectories using genome-wide association studies (GWAS) for measures of growth traits across years in a natural population of Populus tomentosa. By analyzing the stem growth trajectory, we identified PtoP4H9, encoding prolyl 4-hydroxylase 9, which is responsible for the natural variation in the growth rate of diameter at breast height (DBH) across years. Quantifying the dynamic genetic contribution of PtoP4H9 loci to stem growth showed that PtoP4H9 played a pivotal role in stem growth regulation. Spatiotemporal expression analysis showed that PtoP4H9 was highly expressed in cambium tissues of poplars of various ages. Overexpression and knockdown of PtoP4H9 revealed that it altered cell expansion to regulate cell wall modification and mechanical characteristics, thereby promoting stem growth in Populus. We showed that natural variation in PtoP4H9 occurred in a BASIC PENTACYSTEINE transcription factor PtoBPC1-binding promoter element controlling PtoP4H9 expression. The geographic distribution of PtoP4H9 allelic variation was consistent with the modes of selection among populations. Altogether, our study provides important genetic insights into dynamic stem growth in Populus, and we confirmed PtoP4H9 as a potential useful marker for breeding or genetic engineering of poplars.
多年生树木必须在其整个生命周期内维持茎的生长，以随着年龄的增长逐渐增加大小。控制树木茎多年生生长的分子机制的首要问题在很大程度上尚未得到解答。在这里，我们使用全基因组关联研究（GWAS）来解析与毛白杨自然种群多年生长性状相关的遗传结构。通过分析茎的生长轨迹，我们鉴定了编码脯氨酰 4-羟化酶 9（PtoP4H9）的基因，该基因负责胸径（DBH）多年生长速率的自然变异。定量分析 PtoP4H9 基因座对茎生长的动态遗传贡献表明，PtoP4H9 在杨树各年龄段形成层组织中高度表达。PtoP4H9 的时空表达分析表明，它在不同年龄的杨树形成层组织中高表达。过表达和敲低 PtoP4H9 表明，它改变了细胞的扩张，以调节细胞壁的修饰和机械特性，从而促进了杨树的茎生长。我们表明，PtoP4H9 的自然变异发生在 BASIC PENTACYSTEINE 转录因子 PtoBPC1 结合的启动子元件中，该元件控制 PtoP4H9 的表达。PtoP4H9 等位基因变异的地理分布与种群间选择模式一致。总的来说，我们的研究为毛白杨的动态茎生长提供了重要的遗传见解，并证实了 PtoP4H9 作为杨树遗传改良或基因工程的潜在有用标记。
