Betula species constitute a large portion of species in forest ecosystems, are a key player in biomass resources and are recognized as pioneer species with strong stress tolerance. The miR169-NFYA module plays essential roles in the response to abiotic stress, including nutrient stress. However, the functional roles of the miR169-NFYA module in Betula luminifera, an important subtropical and pioneer forestry tree species, in response to nitrogen (N) starvation are not well documented. In the present study, ten BlNFYA genes were identified in B. luminifera. The expression of most BlNFYAs increased under low-nitrogen (LN) stress, while the expression of BlmiR169 was inhibited; among them, BlmiR169c and its corresponding target gene BlNFYA10 might play important regulatory roles in response to N availability. We then functionally investigated BlmiR169c-BlNFYA10 in response to LN stress and determined its regulatory roles in response to N starvation by analyzing the expression patterns, miRNA-mRNA interactions, phenotypes, and physiological and transcriptomic responses of transgenic Arabidopsis and birch roots under LN stress. Overexpression of BlmiR169c and BlNFYA10 resulted in contrasting tolerance to N starvation, and BlNFYA10 provided transgenic plants with LN tolerance with lower growth costs compared with those of the wild type under LN stress. This tolerance might involve a trade-off between growth and defense by upregulating defense- and downregulating photosynthesis- and translation-related activities under LN stress. On the other hand, BlNFYA10 provided transgenic plants with enhanced uptake and assimilation of N, effectively compensating for the defense-growth trade-offs in BlNFYA10-overexpressing plants. Our data demonstrate that a potential regulatory mechanism of BlmiR169c-BlNFYA10 is involved in the LN stress response, providing a basis for increasing the nitrogen-use efficiency (NUE) of B. luminifera and/or other forestry tree species.

桦木物种构成森林生态系统物种的很大一部分，是生物质资源的重要参与者，被公认为具有较强抗逆性的先锋物种。miR169- NFYA模块在对非生物胁迫（包括营养胁迫）的响应中发挥着重要作用。然而，miR169- NFYA模块在Betula luminifera（一种重要的亚热带和先锋林业树种）中对氮 (N) 饥饿的响应的功能作用没有得到很好的记录。在本研究中，在B. luminifera中鉴定了10 个BlNFYA基因。大多数BlNFYA的表达在低氮（LN）胁迫下增加，而BlmiR169被抑制；其中，BlmiR169c及其相应的靶基因BlNFYA10可能在响应 N 可用性方面发挥重要的调节作用。然后，我们从功能上研究了BlmiR169c - BlNFYA10对 LN 胁迫的反应，并通过分析转基因拟南芥和桦树根在 LN 胁迫下的表达模式、miRNA-mRNA 相互作用、表型以及生理和转录组学反应，确定了其对 N 饥饿的调节作用。BlmiR169c和BlNFYA10 的过表达导致对 N 饥饿的对比耐受，而BlNFYA10提供具有 LN 耐受性的转基因植物，与 LN 胁迫下的野生型相比，其生长成本更低。这种耐受性可能涉及在 LN 胁迫下通过上调防御和下调光合作用和翻译相关活动在生长和防御之间的权衡。另一方面，BlNFYA10为转基因植物提供了增强的 N 吸收和同化，有效补偿了BlNFYA10 过表达植物的防御-生长权衡。我们的数据表明BlmiR169c - BlNFYA10的潜在调节机制参与了 LN 应激反应，为提高B. luminifera的氮利用效率 (NUE) 提供了基础 和/或其他林业树种。