Insect-Mediated Modulation of Plant Physiology: The Role of Lignin Biosynthesis and Auxin Signaling in Defense Against Aphids

  • SorghumBase Team
  • 9 December 2024

Insect feeding on plants induces complex physiological and metabolic changes, altering key processes such as photosynthesis, nutrient allocation, and carbohydrate metabolism. Aphid feeding, in particular, has been shown to manipulate these plant functions, affecting resource allocation between source and sink tissues. This interaction also triggers the production of defensive proteins and secondary metabolites, as observed in monocot crops like sorghum. Recent studies highlight that aphid feeding on sorghum plants activates the monolignol biosynthesis pathway, which is associated with plant defense against pests. Specifically, genes like Bmr6 and Bmr12, which are involved in the final steps of monolignol production, are upregulated in response to aphid feeding, potentially disrupting aphid growth and reproduction. However, the effectiveness of these genes varies depending on the context, with differences in resistance observed under laboratory and field conditions.

In this study, scientists from the University of Nebraska-Lincoln and the USDA-ARS explore the role of the lignin biosynthesis gene, Bmr12, in plant defense, which is further complicated by their interactions with phytohormonal pathways. Changes in auxin metabolism, particularly the accumulation of IAA-Asp, were linked to enhanced resistance to aphids in bmr12-mutant sorghum plants. This suggests that auxin signaling plays a significant role in the plant’s defense mechanisms. Interestingly, aphid feeding alters auxin metabolism in a way that promotes plant resistance, independent of the commonly known defense hormones, jasmonic acid (JA) and salicylic acid (SA). This highlights the complexity of plant-insect interactions and suggests that future research should explore how these pathways contribute to broader plant defense strategies.

SorghumBase example: 

Figure 1: SorghumBase’s gene search results for Bmr12. The Germplasm tab shows accessions that harbor predicted loss-of-function alleles (PI 606706, Tift 98bmrB1). The pathways tab zooms in on the role of Bmr12 in the tricin biosynthesis, a flavonoid compound that plays a role in plant defense and stress tolerance.

Reference:

Grover S, Mou DF, Shrestha K, Puri H, Pingault L, Sattler SE, Louis J. Impaired Brown midrib12 function orchestrates sorghum resistance to aphids via an auxin conjugate indole-3-acetic acid-aspartic acid. New Phytol. 2024 Nov;244(4):1597-1615. PMID: 39233513. doi: 10.1111/nph.20091. Read more

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