Many tobacco (Nicotiana tabacum) cultivars are salt-tolerant and thus are potential model plants to study the mechanisms of salt stress tolerance. The CALCINEURIN B-LIKE PROTEIN (CBL) is a vital family of plant calcium sensor proteins that can transmit Ca²⁺ signals triggered by environmental stimuli including salt stress. Therefore, assessing the potential of NtCBL for genetic improvement of salt stress is valuable. In our studies on NtCBL members, constitutive overexpression of NtCBL5A was found to cause salt supersensitivity with necrotic lesions on leaves. NtCBL5A-overexpressing (OE) leaves tended to curl and accumulated high levels of reactive oxygen species (ROS) under salt stress. The supersensitivity of NtCBL5A-OE leaves was specifically induced by Na⁺, but not by Cl⁻, osmotic stress, or drought stress. Ion content measurements indicated that NtCBL5A-OE leaves showed sensitivity to the Na⁺ accumulation levels that wild-type leaves could tolerate. Furthermore, transcriptome profiling showed that many immune response-related genes are significantly upregulated and photosynthetic machinery-related genes are significantly downregulated in salt-stressed NtCBL5A-OE leaves. In addition, the expression of several cation homeostasis-related genes was also affected in salt-stressed NtCBL5A-OE leaves. In conclusion, the constitutive overexpression of NtCBL5A interferes with the normal salt stress response of tobacco plants and leads to Na⁺-dependent leaf necrosis by enhancing the sensitivity of transgenic leaves to Na⁺. This Na⁺ sensitivity of NtCBL5A-OE leaves might result from the abnormal Na⁺ compartmentalization, plant photosynthesis, and plant immune response triggered by the constitutive overexpression of NtCBL5A. Identifying genes and pathways involved in this unusual salt stress response can provide new insights into the salt stress response of tobacco plants.

许多烟草（烟草) 栽培品种具有耐盐性，因此是研究耐盐胁迫机制的潜在模式植物。钙调磷酸酶 B 样蛋白 (CBL) 是重要的植物钙传感器蛋白家族，可传输由环境刺激（包括盐胁迫）触发的Ca ²⁺信号。因此，评估潜力NtCBL对于盐胁迫的遗传改良是有价值的。在我们的研究中NtCBL 成员，组成型过度表达 NtCBL5A 被发现会导致盐分超敏反应，叶片上会出现坏死病变。 NtCBL5A- 过度表达 (OE) 的叶子在盐胁迫下倾向于卷曲并积累高水平的活性氧 (ROS)。超敏反应NtCBL5A-OE 叶片受 Na ⁺特异性诱导，但不受 Cl ^-、渗透胁迫或干旱胁迫的诱导。离子含量测量表明NtCBL5A-OE 叶片对野生型叶片可以耐受的 Na ⁺积累水平表现出敏感性。此外，转录组分析表明，在盐胁迫下，许多免疫反应相关基因显着上调，光合机械相关基因显着下调。NtCBL5A-OE 离开。此外，盐胁迫下几种阳离子稳态相关基因的表达也受到影响。NtCBL5A-OE 离开。总之，本构过表达NtCBL5A通过增强转基因叶片对Na ⁺的敏感性，干扰烟草植物的正常盐胁迫反应并导致Na ⁺依赖性叶片坏死。这 Na ⁺敏感性NtCBL5A-OE 叶子可能是由异常的 Na ⁺区室化、植物光合作用和由组成型过度表达引发的植物免疫反应引起的NtCBL5A. 识别参与这种不寻常的盐胁迫反应的基因和途径可以为烟草植物的盐胁迫反应提供新的见解。