Xiaowen Yao, Xiao Liang, Qing Chen, Ying Liu, Chunling Wu, Mufeng Wu, Jun Shui, Yang Qiao, Yao Zhang, Yue Geng.

Front Plant Sci.; 2023 Jan 6; 13:1067695. doi: 10.3389/fpls.2022.1067695.

Abstract

Introduction: The two-spotted spider mite (TSSM) is a devastating pest of cassava production in China. Lignin is considered as an important defensive barrier against pests and diseases, several genes participate in lignin biosynthesis, however, how these genes modulate lignin accumulation in cassava and shape TSSM-resistance is largely unknown.

Methods: To fill this knowledge gap, while under TSSM infestation, the cassava lignin biosynthesis related genes were subjected to expression pattern analysis followed by family identification, and genes with significant induction were used for further function exploration.

Results: Most genes involved in lignin biosynthesis were up-regulated when the mite-resistant cassava cultivars were infested by TSSM, noticeably, the MePAL gene presented the most vigorous induction among these genes. Therefore, we paid more attention to dissect the function of MePAL gene during cassava-TSSM interaction. Gene family identification showed that there are 6 MePAL members identified in cassava genome, further phylogenetic analysis, gene duplication, cis-elements and conserved motif prediction speculated that these genes may probably contribute to biotic stress responses in cassava. The transcription profile of the 6 MePAL genes in TSSM-resistant cassava cultivar SC9 indicated a universal up-regulation pattern. To further elucidate the potential correlation between MePAL expression and TSSM-resistance, the most strongly induced gene MePAL6 were silenced using virus-induced gene silencing (VIGS) assay, we found that silencing of MePAL6 in SC9 not only simultaneously suppressed the expression of other lignin biosynthesis genes such as 4-coumarate--CoA ligase (4CL), hydroxycinnamoyltransferase (HCT) and cinnamoyl-CoA reductase (CCR), but also resulted in decrease of lignin content. Ultimately, the suppression of MePAL6 in SC9 can lead to significant deterioration of TSSM-resistance.

Discussion: This study accurately identified MePAL6 as critical genes in conferring cassava resistance to TSSM, which could be considered as promising marker gene for evaluating cassava resistance to insect pest.

See https://pubmed.ncbi.nlm.nih.gov/36684737/

Figure 2

The chromosomal locations and phylogeny of MePALs. (A) Chromosomal locations of the six MePAL genes. The chromosomes were presented as narrow rectangles, and color bars within the rectangles denoted the M. esculenta chromosome density. Scale bars on the left indicated the chromosome lengths (Mb); (B) Phylogenetic tree of the 6 MePAL proteins. The tree was constructed by using MEGA X based on the full-length amino acid sequences from M. esculenta (Me) (marked with stars), R. communis (Rc) (marked with circles), H brasiliensis (Hb) (marked with triangles) and A thaliana (At) (marked with boxes). All nodes had significant bootstrap support based on 1,000 replicates. The tree was constructed with cut-off value of 50%. Genes that distributed in the same clusters were shadowed with different colors.