Transcriptome and physiological analyses reveal the response of Arabidopsis thaliana to poly(aspartic acid)

Authors: MACHINGURA, MARYLOU - Georgia Southern University; GLOVER, SIERRA - Georgia Southern University; SETTLES, ALEXIS - Georgia Southern University; Pan, Zhiqiang - Peter; Bajsa-Hirschel, Joanna; CHITIYO, GEORGE - Tennessee Technological University; WEILAND, MITCH - Georgia Southern University

Submitted to: Plant Stress
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/9/2024
Publication Date: 5/24/2024
Citation: Machingura, M.C., Glover, S., Settles, A., Pan, Z., Bajsa Hirschel, J.N., Chitiyo, G., Weiland, M.H. 2024. Transcriptome and physiological analyses reveal the response of Arabidopsis thaliana to poly(aspartic acid). Plant Stress. 12:1-14. https://doi.org/10.1016/j.stress.2024.100478.
DOI: https://doi.org/10.1016/j.stress.2024.100478

Interpretive Summary: Polyaspartic acid (PASP) is an eco-friendly biopolymer used as a fertilizer synergist to enhance agricultural plant growth and improve yields. Although the exact mechanism of PASP enhancement remains unclear, a current hypothesis suggests that the negatively charged polymer helps retain nutrients near the root zone. In this study, Arabidopsis thaliana seeds were germinated and grown in sterile plates containing 250 ppm PASP under continuous light. After 12 days of growth, total RNA was extracted from whole seedlings and sequenced. In addition, physiological assessments revealed significant differences between control and treated plants in leaf area, chlorophyll content, and photosynthetic rate. RNA sequencing identified a total of 462 differentially expressed genes (DEGs), with 245 upregulated and 217 downregulated. Sequence analyses indicated that the DEGs were primarily associated with photosynthesis, as well as other metabolic pathways like phenylpropanoid, nitrogen, and peroxisome metabolism. This information will contribute to our understanding of the biochemical pathways involved in plant responses to PASP.

Technical Abstract: Poly(aspartic acid) (PASP) is an environmentally friendly biopolymer used as a fertilizer synergist and known to increase agricultural yields. The mechanism of PASP enhancement has, however, not been established, although the general hypothesis is that the polymer functions to hold nutrients closer to the root zone. The objective of this study was to determine the physiological and molecular changes that occur when plants are exposed to PASP, with future directions leading to a proposed mode of action. A whole genome transcriptome study was conducted. Arabidopsis thaliana seeds were germinated and grown in sterile plates treated with 250 ppm PASP under continuous light. Total RNA was extracted from whole seedlings and sequenced. The results revealed 462 differentially expressed genes (DEGs), 245 of which were upregulated and 217 downregulated. Gene Ontology, KEGG and MAPman analyses revealed DEGs involved in photosynthesis with 11 light harvesting complexes upregulated (e.g. LHCB1.1, LHCB2.2, LHCA1, LHCB4.2, LHCB2.1, LHCA4, LHCB1.1, LHCB3, LHCA3); the peroxisome pathway had 6 DEGs (CAT1, KAT1 and XDH2) upregulated (CSD1, CSD2 and FSD2) downregulated, the phenylpropanoid biosynthesis pathway had 7 DEGs upregulated. Other key DEGs were associated with the amino acid (e.g. ASN1) and nitrogen metabolism pathways. Physiology assessment results showed significant differences between control and treated plants with a 33 % increase in leaf area, 25 % increase chlorophyll content (p = 0.05) and a 4-fold increase in photosynthetic rate (p = 0.001). This information helps to increase our understanding of the key genes and metabolic pathways associated with plant response to PASP.