Transcriptional Regulation of SugarCane Response to Sporisorium scitamineum: Insights from Time-Course Gene Coexpression and Ca2+ Signaling

Sugarcane response to Sporisorium scitamineum is determined by multiple major genes and numerous microeffector genes. Here, time-ordered gene coexpression networks were applied to explore the interaction between sugarcane and S. scitamineum. Totally, 2459 differentially expressed genes were identified and divided into 10 levels, and several stress-related subnetworks were established. Interestingly, the Ca2+ signaling pathway was activated to establish the response to sugarcane smut disease. Accordingly, two CAX genes (ScCAX2 and ScCAX3) were cloned and characterized from sugarcane. They were significantly upregulated under ABA stress but inhibited by MeJA treatment. Furthermore, overexpression of ScCAX2 and ScCAX3 enhanced the susceptibility of transgenic plants to the pathogen infection, suggesting its negative role in disease resistance. A regulatory model for ScCAX genes in disease response was thus depicted. This work helps to clarify the transcriptional regulation of sugarcane response to S. scitamineum stress and the function of the CAX gene in disease response.甘蔗对甘蔗黑粉菌（Sporisorium scitamineum）的响应由多个主效基因以及大量微效应基因（microeffector genes）所决定。本研究借助时序基因共表达网络（time-ordered gene coexpression networks）探究了甘蔗与S. scitamineum之间的互作关系，共计鉴定得到2459个差异表达基因（differentially expressed genes），并将其划分为10个表达层级，同时构建了多个胁迫相关子网。值得注意的是，钙信号通路（Ca2+ signaling pathway）被激活以建立对甘蔗黑穗病的响应。据此，本研究从甘蔗中克隆并鉴定了两个钙交换蛋白基因（CAX genes）：ScCAX2与ScCAX3。二者在脱落酸（ABA）胁迫下显著上调表达，但经茉莉酸甲酯（MeJA）处理后其表达受到抑制。进一步研究发现，过表达（overexpression）ScCAX2与ScCAX3会增强转基因植物（transgenic plants）对病原菌侵染（pathogen infection）的敏感性，表明其在抗病性中发挥负调控作用。本研究由此构建了ScCAX基因在病害响应中的调控模型。该研究有助于阐明甘蔗对S. scitamineum胁迫的转录调控（transcriptional regulation）机制，以及CAX基因在病害响应中的具体功能。