Overexpression of the monolignol pathway gene SbCCoAOMT enhances sorghum resistance to sugarcane aphid through increased lignin deposition, altered phloem-feeding behavior, and accumulation of defensive phenolic compounds.

Keywords: CCoAOMT, electrophysiology, hydroxycinnamic acids, plant defense, sorghum, sugarcane aphids

The sugarcane aphid (SCA), Melanaphis sacchari, poses a major threat to sorghum production through sustained phloem feeding, which impairs plant growth and yield. Widely adopted strategies for managing SCA include applying insecticides and growing sorghum varieties with genetic resistance. Research indicates that properly leveraging host plant resistance offers one of the most cost-effective, environmentally safe, and efficient approaches to pest management. Researchers from University of Nebraska-Lincoln investigated the defensive role of SbCCoAOMT, a gene associated with the monolignol biosynthesis pathway, in enhancing sorghum resistance to SCA. Aphid feeding was shown to induce SbCCoAOMT expression, leading to elevated lignin accumulation—a structural barrier that can deter insect feeding. Overexpression of SbCCoAOMT conferred both antibiosis and antixenosis, as evidenced by altered aphid behavior and reduced feeding success in bioassays. Electropenetrography analysis revealed decreased time spent in the sieve element phase by aphids on overexpressing plants, suggesting activation of phloem-based defenses.

Biochemical analyses further showed that SbCCoAOMT overexpression increased levels of ferulic and sinapic acids—hydroxycinnamic compounds with known antioxidant and potential insect-deterrent properties. Feeding assays supplemented with these phenolics demonstrated significant negative effects on SCA survival and reproduction, suggesting their role in plant defense. While SbCCoAOMT overexpression did not significantly alter global gene expression profiles, it modulated phenylpropanoid-related pathways in a way that enhanced resistance without compromising plant development. The parallels drawn with similar genes in maize and wheat reinforce the broader applicability of lignin-associated defense strategies. These findings underscore the value of targeting cell wall biosynthesis genes like SbCCoAOMT to improve integrated pest management and warrant further investigation into the molecular underpinnings of phloem-based and chemical defenses in sorghum.

SorghumBase examples:

SbCCoAOMT (SORBI_3010G052200)

Figure 1: Phylogenetic tree view from the Homology tab for the gene SbCCoAOMT (SORBI_3010G052200) in SorghumBase, visualized using Ensembl Compara.This tree illustrates the evolutionary relationships between Caffeoyl-CoA O-methyltransferase 2 (CCoAOMT2) in Sorghum bicolor and its homologs across multiple sorghum accessions and related grass species.This tree helps confirm gene family conservation and divergence, key for interpreting functional redundancy or specialization in stress-response pathways such as lignin biosynthesis.
Figure 2: Germplasm variation at the SbCCoAOMT locus (SORBI_3010G052200) in Sorghum bicolor BTx623, visualized through the Germplasm tab on SorghumBase. This figure highlights natural variation in the SbCCoAOMT gene across diverse sorghum accessions. Germplasm lines carrying predicted transcript variants (PTVs)—including missense and nonsense mutations—are shown, offering insight into functional diversity of this lignin biosynthesis gene. These genetic differences may influence resistance to sugarcane aphids and are valuable for breeding efforts targeting durable pest resistance.
Reference:

Ikuze E, Grover S, Puri H, Kundu P, Sattler S, Louis J. Overexpression of the Sorghum CCoAOMT Gene Confers Enhanced Resistance to Sugarcane Aphids. Physiol Plant. 2025 May-Jun;177(3):e70291. PMID: 40405540. doi: 10.1111/ppl.70291. Read more

Related Project Websites: 

 

Monolignol Pathway-Mediated Resistance to Sugarcane Aphid in Sorghum

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