Crustacean meal elicits expression of growth and defense-related genes in roots of lettuce and tomato

Authors: Kandel, Shyam; Anchieta, Amy; SHI, AINONG - University Of Arkansas; Mou, Beiquan; Klosterman, Steven

Submitted to: PhytoFrontiers
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/29/2021
Publication Date: 1/19/2022
Citation: Kandel, S.L., Anchieta, A.G., Shi, A., Mou, B., Klosterman, S.J. 2022. Crustacean meal elicits expression of growth and defense-related genes in roots of lettuce and tomato. Phytofrontiers. 2(1):10-20. https://doi.org/10.1094/PHYTOFR-03-21-0017-R.
DOI: https://doi.org/10.1094/PHYTOFR-03-21-0017-R

Interpretive Summary: Synthetic pesticides have been commonly used to improve the agricultural productivity and to manage insect pests and diseases. However, the continued use usage of synthetic pesticides may have adverse consequences to human and animal health and may lead to the emergence of pesticide resistant strains of plant pathogens. Therefore, research efforts are also focused on the analyses of naturally occurring compounds that promote plant health. Chitin, a naturally occurring compound derived from crustacean shells, has been primarily utilized as a soil amendment to improve soil microbiomes and to promote defense in plants, thereby mitigating the various biotic and abiotic stresses. In the study, crabshell chitin was applied to roots of lettuce and tomato plants and the gene expression in response to chitin treatment was characterized. This research revealed marked differences in expression levels between the genes induced in lettuce and tomato, and some overlap in those genes induced that encode enzymes that have roles in cell wall strengthening, suggesting chitin may stimulate this response in both lettuce and tomato. Induction of enzymes involved in cell wall strengthening in roots may be an important component of defense. An increased understanding of how naturally occurring compounds such as chitin function to promote plant health is critically important for their deployment.

Technical Abstract: Chitin, a polymer of N-acetylglucosamine, and derivatives of this polymer have been used widely as elicitors of plant defense responses. However, the types of defenses deployed in plant roots in response to chitin are not well understood. In this study, crab shell chitin was applied to lettuce and tomato roots in which the seedlings were grown on a sterile glass wool substrate in Hoagland’s solution. Induction of gene expression was assessed by RNA sequencing (RNAseq) at 24 h after application relative to a 0 hr time point. The RNAseq analyses revealed upregulation of different types of genes in both tomato and lettuce roots at 24 h. While there was predominantly increased expression of known genes associated with oxidoreductases/metal ion binding in tomato at 24 h, there was predominantly increased expression of genes associated with cell wall organization and hydrolases in lettuce roots at 24 h. The types of defense-related genes expressed in root tissues of each of the two plant species was also markedly different. Interestingly, genes related to phenylpropanoid pathway responsible for biosynthesis of lignin were significantly upregulated in both lettuce and tomato roots. Chitin induced lignification and strengthening of the plant cell wall is perhaps a broad-spectrum defense mechanism in plant roots. This research provides insight into gene expression patterns in the roots of two very different types of crop plants in response to chitin, improving our understanding of how this molecule aids in plant health.