Oxygen sensing and adaptation to hypoxia in Medicago truncatula nodules

蒺藜苜蓿根瘤的氧传感和缺氧适应

• 批准号: BB/Y000226/1
• 负责人: Francesco Licausi
• 金额: $ 65.98万
• 依托单位: University of Oxford
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2023
• 资助国家: 英国
• 起止时间: 2023 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=BB%2FY000226%2F1
• 关键词: Oxygen; sensing; adaptation; hypoxia; Medicago

Apart from carbon and oxygen, plants need to extract their nutrients from the soil where their roots grow. Nitrogen and phosphorous are the main limiting elements for crop growth and yield and thus farmers replenish the soil with fertilizers. However, soil fertilization causes sustainability problems, since the nitrogen forms usable by plants, nitrate and ammonia, require high energy inputs from non-renewable resources to be synthesized. Moreover, fertilisers are subjected to leaching by rainwater and when they reach waterbodies they pose threats for human consumption and eutrophication. An alternative, or at least an integration, to soil fertilization is the promotion of symbiotic interactions with microorganisms able to carry out nitrogen fixation in exchange for carbon from the plant. Several species from the plant family of legumes can establish such an interaction. Thus, crops belonging to this group not only thrive even when nitrogen is limiting, but they are also used in rotations to replenish soil with nitrogen. The nitrogen fixing bacteria require high energy but also very low oxygen levels, since this molecule is poisonous for the enzyme that carries out this reaction. To accommodate these needs, legume roots form a specific organ, called nodule, to host the bacteria. In the nodule, the diffusion of free oxygen is severely limited, and channelled towards energy producing organelles, preventing damage to the nitrogen-fixing enzymes. We want to understand how the cells in this organ cope with low oxygen conditions, and how they use the information about oxygen availability to establish symbiosis with nitrogen-fixing bacteria. Finally, we plan to study how the nodule senses and responds when oxygen is poorly available in the environment, as it happens in case of soil waterlogging. The knowledge generated with this project will support the breeding of new legume varieties, able to support nitrogen fixation even in case of low oxygen in soil. Our results will also support other researchers to devise strategies to engineer this process in other plant species.

除了碳和氧之外，植物还需要从根部生长的土壤中提取养分。氮和磷是作物生长和产量的主要限制元素，因此农民用肥料补充土壤。然而，土壤施肥会带来可持续性问题，因为植物可利用的氮形式、硝酸盐和氨需要来自不可再生资源的大量能量输入才能合成。此外，化肥会被雨水淋滤，当它们到达水体时，会对人类消耗和富营养化构成威胁。土壤施肥的一种替代方案或至少是一种整合是促进与能够进行固氮以换取植物碳的微生物的共生相互作用。豆科植物中的几个物种可以建立这种相互作用。因此，属于这一类的作物不仅在氮肥有限的情况下也能茁壮成长，而且还可以轮作来补充土壤的氮肥。固氮细菌需要高能量，但也需要非常低的氧气含量，因为这种分子对于进行该反应的酶是有毒的。为了满足这些需求，豆科植物的根部形成了一个称为根瘤的特定器官来容纳细菌。在根瘤中，游离氧的扩散受到严格限制，并被引导至产生能量的细胞器，从而防止对固氮酶的损害。我们想了解该器官中的细胞如何应对低氧条件，以及它们如何利用有关氧气可用性的信息来与固氮细菌建立共生。最后，我们计划研究当环境中氧气不足时，结核如何感知和响应，就像在土壤涝灾的情况下一样。该项目产生的知识将支持新豆类品种的培育，即使在土壤低氧的情况下也能够支持固氮。我们的结果还将支持其他研究人员制定策略，在其他植物物种中设计这一过程。