Hillabrand R M, Gordon H, Hynes B, Constabel C P, Landhäusser S M
Department of Renewable Resources, University of Alberta, 442 ESB, Edmonton, Alberta, T6G 2E3, Canada.
Centre for Forest Biology & Department of Biology, University of Victoria, 3800 Finnerty Road, V8P 5C2, Victoria, British Columbia, Canada.
Tree Physiol. 2023 Feb 21. doi: 10.1093/treephys/tpad020.
Remobilization of carbon storage compounds in trees is crucial for the resilience to disturbances, stress, and the requirements of their perennial lifestyle, all of which can impact photosynthetic carbon gain. Trees contain abundant non-structural carbohydrates (NSC) in the form of starch and sugars for long term carbon storage, yet questions remain about the ability of trees to remobilize non-conventional carbon compounds under stress. Aspens, like other members of the genus Populus, have abundant specialized metabolites called salicinoid phenolic glycosides, which contain a core glucose moiety. In this study, we hypothesized that the glucose-containing salicinoids could be remobilized as an additional carbon source during severe carbon limitation. We made use of genetically modified hybrid aspen (Populus tremula x P. alba) with minimal salicinoid content and compared these to control plants with high salicinoid content during resprouting (suckering) in dark (carbon limited) conditions. As salicinoids are abundant anti-herbivore compounds, identification of such a secondary function for salicinoids may provide insight to the evolutionary pressures that drive their accumulation. Our results show that salicinoid biosynthesis is maintained during carbon limitation and suggests that salicinoids are not remobilized as a carbon source for regenerating shoot tissue. However, we found that salicinoid-producing aspens had reduced resprouting capacity per available root biomass when compared to salicinoid-deficient aspens. Therefore, our work shows that the constitutive salicinoid production in aspens can reduce the capacity for resprouting and survival in carbon limited conditions.
树木中碳储存化合物的再调动对于其抵御干扰、压力以及适应多年生生活方式的需求至关重要，所有这些都会影响光合碳的获取。树木以淀粉和糖的形式含有丰富的非结构性碳水化合物（NSC）用于长期碳储存，但关于树木在压力下调动非常规碳化合物的能力仍存在疑问。与杨属的其他成员一样，白杨含有丰富的特殊代谢产物，称为水杨苷类酚糖苷，其含有核心葡萄糖部分。在本研究中，我们假设在严重碳限制期间，含葡萄糖的水杨苷类化合物可以作为额外的碳源被调动。我们利用水杨苷类含量极低的转基因杂交白杨（欧洲山杨×银白杨），并在黑暗（碳限制）条件下重新发芽（萌蘖）期间将其与水杨苷类含量高的对照植物进行比较。由于水杨苷类是丰富的抗食草动物化合物，确定水杨苷类的这种次要功能可能有助于了解驱动其积累的进化压力。我们的结果表明，在碳限制期间水杨苷类生物合成得以维持，这表明水杨苷类不会作为再生茎组织的碳源被调动。然而，我们发现与缺乏水杨苷类的白杨相比，产生水杨苷类的白杨每单位可用根生物量的重新发芽能力降低。因此，我们的研究表明，白杨中组成型水杨苷类的产生会降低在碳限制条件下的重新发芽能力和存活率。
