Department of Crop and Soil Sciences, Washington State University, Pullman, WA, 99164, USA.
Molecular Plant Sciences Graduate Group, Washington State University, Pullman, WA, 99164, USA.
BMC Genomics. 2024 Aug 29;25(1):816. doi: 10.1186/s12864-024-10648-w.
CINNAMYL ALCOHOL DEHYDROGENASE (CAD) catalyzes the NADPH-dependent reduction of cinnamaldehydes into cinnamyl alcohols and is a key enzyme found at the final step of the monolignol pathway. Cinnamyl alcohols and their conjugates are subsequently polymerized in the secondary cell wall to form lignin. CAD genes are typically encoded by multi-gene families and thus traditionally organized into general classifications of functional relevance.
In silico analysis of the hexaploid Triticum aestivum genome revealed 47 high confidence TaCAD copies, of which three were determined to be the most significant isoforms (class I) considered bone fide CADs. Class I CADs were expressed throughout development both in RNAseq data sets as well as via qRT-PCR analysis. Of the 37 class II TaCADs identified, two groups were observed to be significantly co-expressed with class I TaCADs in developing tissue and under chitin elicitation in RNAseq data sets. These co-expressed class II TaCADs were also found to be phylogenetically unrelated to a separate clade of class II TaCADs previously reported to be an influential resistance factor to pathogenic fungal infection. Lastly, two groups were phylogenetically identified as class III TaCADs, which possess distinct conserved gene structures. However, the lack of data supporting their catalytic activity for cinnamaldehydes and their bereft transcriptional presence in lignifying tissues challenges their designation and function as CADs.
Taken together, our comprehensive transcriptomic analyses suggest that TaCAD genes contribute to overlapping but nonredundant functions during T. aestivum growth and development across a wide variety of agroecosystems and provide tolerance to various stressors.
肉桂醇脱氢酶（CAD）催化肉桂醛在 NADPH 依赖性条件下还原为肉桂醇，是木质素单体途径的最后一步中发现的关键酶。肉桂醇及其共轭物随后在次生细胞壁中聚合形成木质素。CAD 基因通常由多基因家族编码，因此传统上按照功能相关性进行分类。
对六倍体小麦（Triticum aestivum）基因组的计算机分析显示，有 47 个高可信度的 TaCAD 拷贝，其中 3 个被确定为最重要的同工型（I 类），被认为是真正的 CAD。I 类 CAD 在发育过程中通过 RNAseq 数据集以及 qRT-PCR 分析均有表达。在鉴定的 37 个 II 类 TaCAD 中，有两个亚类在发育组织中与 I 类 TaCAD 显著共表达，并且在 RNAseq 数据集中受到几丁质诱导。这些共表达的 II 类 TaCAD 与先前报道的对致病真菌感染有影响的抗性因子的一个独立的 II 类 TaCAD 分支在系统发育上没有关系。最后，两个亚类被鉴定为 III 类 TaCAD，它们具有独特的保守基因结构。然而，缺乏支持它们对肉桂醛的催化活性以及在木质化组织中缺乏转录存在的数据，对它们作为 CAD 的指定和功能提出了挑战。
总的来说，我们全面的转录组学分析表明，TaCAD 基因在多种农业生态系统中对小麦的生长和发育有重叠但非冗余的作用，并为各种胁迫提供了耐受性。
