# Transcription, Alternative Splicing, and Post-Translational Regulation of CaLOXs in the Dynamic Regulation of Jasmonate Levels in Wounded Pepper Leaves

## TL;DR

The study explores how jasmonate levels in pepper leaves change after wounding, focusing on gene expression, splicing, and enzyme regulation.

## Contribution

The paper reveals how CaLOX gene variants and splicing events dynamically regulate jasmonate levels in response to plant wounding.

## Key findings

- CaLOX2 shows rapid but short-lived wound-induced expression due to a phosphosite Ser residue.
- CaLOX7 has higher wound-induced expression at 6 h due to a non-phosphorylatable Ala residue.
- Exon 4 retention in CaLOX8 transcripts may reduce enzyme activity by blocking the active site.

## Abstract

In response to stresses, jasmonates increase rapidly, leading to plant resistance against necrotrophic pathogens and chewing insect herbivores. Jasmonate biosynthesis is regulated at many levels, including transcriptionally, through alternative splicing, and the phosphorylation of the 13S-lipoxygenase (LOX) that catalyzes an early step in jasmonate biosynthesis. In pepper, transcriptomic analysis of a foliar wounding time course was conducted to deepen our understanding of these regulatory mechanisms. All four CaLOXs are constitutively expressed. CaLOX2, which encodes an enzyme with a Ser in a predicted regulatory phosphosite, shows a rapid but short-lived increase in wound-induced expression. In contrast, CaLOX7, which encodes a protein with a non-phosphorylatable Ala at the phosphosite, shows higher wound-induced expression at 6 h. As well, at this timepoint, there is a predicted increase in exon 4 retention in CaLOX8 transcripts in wounded plants. ChimeraX protein modeling predicts that the retention of exon 4 may negatively affect enzyme activity, possibly by blocking access to the enzyme’s active site. The transcription, alternative splicing, and post-translational regulation of CaLOX enzymes support the dynamic fluctuations observed in the jasmonates, which increase rapidly upon wounding and return to basal levels at 6 h post-stress.