Systematic Analysis of Cinnamyl Alcohol Dehydrogenase Family in Cassava and Validation of MeCAD13 and MeCAD28 in Lignin Synthesis and Postharvest Physiological Deterioration

Cassava (Manihot esculenta Crantz) is used as a biomass energy material and an effective supplement for food and feed. Cinnamyl alcohol dehydrogenase (CAD) catalyzes the final step of lignin biosynthesis and is responsible for various stresses. However, systematic investigations of the CAD gene family in cassava have been poorly understood. In this study, a genome-wide survey and bioinformatics analysis of CAD gene family was performed, transcriptomics, qRT-PCR, gene silencing and stress of yeast cell were used for excavate and validate the candidate MeCADs gene. 36 MeCADs genes unevenly distributed across 12 chromosomes were identified. Through phylogenetic analyses alongside their Arabidopsis counterparts, these MeCADs were divided into four groups, each containing a similar structure and conserved motifs. Interestingly, transcriptome data analysis revealed that 32 MeCAD genes were involved in the postharvest physiological deterioration (PPD) process, whereas 27 MeCAD genes showed significant changes. Additionally, the relative quantitative analysis of 6 MeCAD genes demonstrated that they were sensitive to PPD, suggesting that they may be involved in the regulation of PPD. Silencing MeCAD13 and MeCAD28 further showed that lignin content significantly decreased in the leaves. The wound-stress tolerance of transgenic yeast cells was enhanced after transformation with MeCAD13 and MeCAD28. MeCAD13 and MeCAD28 may play positive roles in lignin biosynthesis and PPD response, respectively. These results provided a systematic functional analysis of MeCADs in cassava and paved a new way to genetically modify lignin biosynthesis and PPD tolerance.