Data from: Recombinant DNA modification of gibberellin metabolism alters growth rate and biomass allocation in Populus

Overexpression of genes that modify gibberellin (GA) metabolism and signaling have been previously shown to produce trees with improved biomass production but highly disturbed development. To examine if more subtle types of genetic modification of GA could improve growth rate and modify tree architecture, we transformed a model poplar genotype (Populus tremula × P. alba) with eight genes, including two cisgenes (intact copies of native genes), four intragenes (modified copies of native genes), and two transgenes (from sexually incompatible species), and studied their effects under greenhouse and field conditions. In the greenhouse, four out of the eight tested genes produced a significant and often striking improvement of stem volume, and two constructs significantly modified the proportion of root or shoot biomass. Characterization of GA concentrations in the cisgenic population that had an additional copy of a poplar GA20-oxidase gene showed elevated concentrations of 13-hydroxylated GAs compared to wild-type poplars. In the field, we observed growth improvement for three of the six tested constructs, but it was significantly greater for only one of the constructs, a pRGL:GA20-oxidase intragene. The greenhouse and field responses were highly variable, possibly to due to cross-talk among the GA pathway and other stress response pathways, or due to interactions between the cisgenes and intragenes with highly similar endogenes. Our results indicate that extensive field trials, similar to those required for conventional breeding, will be critical to evaluating the value and pleiotropic effects of GA-modifying genes.此前已有研究证实，修饰赤霉素（gibberellin，GA）代谢与信号通路的基因过表达，可使树木生物量提升，但会严重扰乱其生长发育。为探究更为温和的赤霉素遗传修饰方式能否提升树木生长速率并改变株型，本研究以模式杨树基因型（Populus tremula × P. alba）为转化受体，引入8个基因构件：其中2个为顺式基因（cisgene，完整的内源基因拷贝）、4个为内源修饰基因（intragene，经修饰的内源基因拷贝），剩余2个为转基因（transgene，来自有性不亲和物种的外源基因），并在温室与田间两种试验环境下分析了这些基因的调控效应。温室试验中，8个被测基因构件中有4个可显著且往往极为显著地提升茎秆体积，另有2个构件可显著改变根系或地上部的生物量分配比例。对携带额外杨树GA20氧化酶（GA20-oxidase）基因拷贝的顺式转基因群体进行赤霉素浓度表征分析后发现，其13-羟基化赤霉素类物质的浓度较野生型杨树显著升高。田间试验中，6个被测基因构件中有3个可实现生长速率提升，但仅1个构件——即pRGL:GA20氧化酶内源修饰基因——的生长提升效果极为显著。温室与田间的试验响应差异极大，这可能源于赤霉素信号通路与其他胁迫响应通路间的信号串扰，或是顺式基因与携带高度相似内源基因的内源修饰基因之间的互作。本研究结果表明，与传统育种所需的大规模田间试验一致，开展大范围田间试验对于评估赤霉素修饰基因的应用价值与多效性效应至关重要。