BBX transcription factors play vital roles in plant growth, development, and stress responses. Although BBX proteins have been studied in great detail in the model plant Arabidopsis, their roles in crop plants such as chrysanthemum are still largely uninvestigated. Here, we cloned CmBBX22 and further determined the function of CmBBX22 in response to drought treatment. Subcellular localization and transactivation assay analyses revealed that CmBBX22 was localized in nucleus and possessed transactivation activity. Overexpression of CmBBX22 in chrysanthemum was found to reduce plant drought tolerance, whereas expression of the chimeric repressor CmBBX22-SRDX was found to promote a higher drought tolerance than that shown by wild-type plants, indicating that CmBBX22 negatively regulates drought tolerance in chrysanthemum. Transcriptome analysis and physiological measurements indicated the potential involvement of CmBBX22-mediated ABA response, stomatal conductance and antioxidant responses in the negative regulation of drought tolerance in chrysanthemum. Based on the findings of this study, we were thus able to establish the mechanisms whereby the transcriptional activator CmBBX22 negatively regulates drought tolerance in chrysanthemum via the regulation of ABA response, stomatal conductance and antioxidant responses.

中文翻译：

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BBX基因CmBBX22负调控菊花的干旱胁迫耐受性

BBX 转录因子在植物生长、发育和胁迫反应中起着至关重要的作用。尽管 BBX 蛋白已在模式植物拟南芥中进行了非常详细的研究，但它们在菊花等农作物中的作用在很大程度上仍未得到研究。在这里，我们克隆了 CmBBX22 并进一步确定了 CmBBX22 响应干旱处理的功能。亚细胞定位和反式激活分析表明，CmBBX22 定位于细胞核并具有反式激活活性。发现 CmBBX22 在菊花中的过表达会降低植物的耐旱性，而嵌合阻遏物 CmBBX22-SRDX 的表达被发现会促进比野生型植物更高的耐旱性，表明 CmBBX22 负向调节菊花的耐旱性。转录组分析和生理测量表明 CmBBX22 介导的 ABA 反应、气孔导度和抗氧化反应可能参与了菊花耐旱性的负调节。基于这项研究的发现，我们因此能够建立转录激活因子 CmBBX22 通过调节 ABA 反应、气孔导度和抗氧化反应来负向调节菊花耐旱性的机制。