Department of Physiology and Cell Biology, Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), Gatersleben, Germany.
Plant Physiology, University Kaiserslautern, Kaiserslautern, Germany.
Physiol Plant. 2022 Sep;174(5):e13776. doi: 10.1111/ppl.13776.
Boron (B) deficiency is a highly prominent nutrient disorder. While B-efficient accessions have recently been identified in the highly B-demanding crop oilseed rape, it remained unclear which physiological processes underlie B efficiency and which signaling pathways trigger an efficient B-deficiency response. Here, we compared, under three different B supply conditions, two Brassica napus accessions with contrasting B efficiency. Shoot biomass formation, B distribution patterns and metabolic dynamics of different phytohormone species were studied using a combination of mass spectrometry-based analyses and physiological measurements. Our results show that the B-efficient accession CR2267 does not differ from the B-inefficient accession CR2262 in terms of B accumulation and subcellular B-partitioning, although it displays no morphological B-deficiency symptoms under severe B-deficient conditions. Investigating phytohormone metabolism revealed a strong accumulation of cytokinins in CR2267 at a developmental stage when striking B-dependent differences in biomass and organ formation emerge in the two B. napus accessions. In contrast, elevated levels of the stress hormone abscisic acid as well as bioactive auxins, representing functional antagonists of cytokinins in shoots, were detected only in CR2262. Our results indicate that superior B efficiency in CR2267 relies on a higher B utilization efficiency that builds on an earlier and higher cytokinin biosynthesis required for the maintenance of the shoot meristem activity and proper leaf development. We further conclude that an elevated abundance of cytokinins is not a consequence of better plant growth but rather a presumption for better plant growth under low-B conditions.
硼（B）缺乏是一种高度突出的营养失调症。虽然最近在对硼需求量高的作物油菜中已经鉴定出了高效硼的品种，但仍不清楚哪些生理过程是硼效率的基础，哪些信号通路触发了有效的硼缺乏响应。在这里，我们在三种不同的硼供应条件下，比较了两个具有不同硼效率的甘蓝型油菜品种。使用基于质谱的分析和生理测量相结合的方法，研究了不同植物激素种类的芽生物量形成、硼分布模式和代谢动态。我们的结果表明，高效硼品种 CR2267 在硼积累和亚细胞硼分配方面与低效硼品种 CR2262 没有差异，尽管在严重缺硼条件下，它没有表现出明显的形态缺硼症状。研究植物激素代谢发现，在两个油菜品种出现生物量和器官形成的显著硼依赖差异的发育阶段，CR2267 中细胞分裂素的积累很强。相比之下，在 CR2262 中仅检测到应激激素脱落酸和生物活性生长素的水平升高，生长素是芽中细胞分裂素的功能拮抗剂。我们的结果表明，CR2267 具有较高的硼效率，这依赖于更高的硼利用效率，而这种效率建立在维持芽分生组织活性和适当叶片发育所需的更早和更高的细胞分裂素生物合成之上。我们进一步得出结论，细胞分裂素的丰度增加不是更好的植物生长的结果，而是在低硼条件下更好的植物生长的前提。
