Yao Xiaowen, Liang Xiao, Chen Qing, Liu Ying, Wu Chunling, Wu Mufeng, Shui Jun, Qiao Yang, Zhang Yao, Geng Yue
Environment and Plant Protection Institute, Chinese Academy of Tropical Agricultural Sciences/Key Laboratory of Integrated Pest Management on Tropical Crops, Ministry of Agriculture and Rural Affairs, Haikou, Hainan, China.
Sanya Research Academy, Chinese Academy of Tropical Agriculture Science/Hainan Key Laboratory for Biosafety Monitoring and Molecular Breeding in Off-Season Reproduction Regions, Sanya, Hainan, China.
Front Plant Sci. 2023 Jan 6;13:1067695. doi: 10.3389/fpls.2022.1067695. eCollection 2022.
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.
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.
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.
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.
二斑叶螨是中国木薯生产中的一种毁灭性害虫。木质素被认为是抵御病虫害的重要防御屏障，有几个基因参与木质素生物合成，然而，这些基因如何调节木薯中木质素的积累以及形成抗二斑叶螨能力在很大程度上尚不清楚。
为填补这一知识空白，在二斑叶螨侵染下，对木薯木质素生物合成相关基因进行表达模式分析，随后进行家族鉴定，并对诱导显著的基因进行进一步功能探索。
抗螨木薯品种受二斑叶螨侵染时，大多数参与木质素生物合成的基因上调，值得注意的是，MePAL基因在这些基因中诱导最为强烈。因此，我们更关注解析MePAL基因在木薯 - 二斑叶螨互作过程中的功能。基因家族鉴定表明，在木薯基因组中鉴定出6个MePAL成员，进一步的系统发育分析、基因复制、顺式元件和保守基序预测推测这些基因可能有助于木薯的生物胁迫响应。抗二斑叶螨木薯品种SC9中6个MePAL基因的转录谱显示出普遍上调模式。为进一步阐明MePAL表达与抗二斑叶螨能力之间的潜在相关性，使用病毒诱导基因沉默（VIGS）试验沉默诱导最强的基因MePAL6，我们发现SC9中MePAL6的沉默不仅同时抑制了其他木质素生物合成基因如4 - 香豆酸 - CoA连接酶（4CL）、羟基肉桂酰转移酶（HCT）和肉桂酰 - CoA还原酶（CCR）的表达，还导致木质素含量降低。最终，SC9中MePAL6的抑制会导致抗二斑叶螨能力显著下降。
本研究准确鉴定出MePAL6是赋予木薯抗二斑叶螨能力的关键基因，可被视为评估木薯抗虫性的有前景的标记基因。
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