# Functional Characterization of CaSpr2 in Jasmonate-Dependent Induced Defense Against Western Flower Thrips in Capsicum annuum

## TL;DR

This study identifies a gene in peppers that helps defend against a harmful insect pest by regulating a key plant defense pathway.

## Contribution

The study reveals CaSpr2 as a novel regulator in the jasmonic acid pathway critical for pepper resistance to western flower thrips.

## Key findings

- Silencing CaSpr2 reduced jasmonic acid levels and increased pepper susceptibility to western flower thrips.
- Thrips on CaSpr2-silenced plants showed improved fitness, including longer lifespan and higher reproduction rates.
- CaSpr2 is essential for pepper resistance to thrips through its role in the jasmonic acid signaling pathway.

## Abstract

Insect pests, such as the western flower thrip (WFT), poses a significant threat to global agriculture by damaging crops and reducing yield. Although the jasmonic acid (JA) signaling pathway is known to be involved in plant defense against WFTs, the key molecular components of this pathway in non-model crops like pepper remain poorly understood. This study functionally characterizes the role of suppressor of prosystemin-mediated responses2 (Spr2) in defense response against WFTs in pepper. We demonstrated that silencing CaSpr2 accumulated lower levels of JA and jasmonoyl-isoleucine (JA-Ile), and exhibited enhanced susceptibility to WFTs. Moreover, WFT individuals on CaSpr2-silenced plants exhibited enhanced fitness, including prolonged adult longevity, increased fecundity, and accelerated population growth. Our findings establish CaSpr2 as a crucial regulator within the JA-mediated signaling pathway that is essential for resistance to WFTs in pepper. This knowledge provides a valuable genetic target for breeding improved pepper cultivars with enhanced and sustainable pest resistance, potentially reducing reliance on chemical pesticides.

Insect infestation poses a significant threat to global agriculture by impairing plant growth and reducing crop yields. The western flower thrip (WFT) causes substantial damage through both direct feeding and transmission of plant viruses. Although the jasmonic acid (JA) signaling pathway is known to participate in plant defense against WFTs, the underlying molecular mechanisms in non-model crops such as peppers, remain largely elusive. This study investigates the role of suppressor of prosystemin-mediated responses2 (Spr2) within JA-mediated defense against WFTs in pepper. Through an integrated approach employing virus-induced gene silencing (VIGS), transcription analysis, phytohormone quantification, insect behavior assays and life history investigations, we demonstrated that silencing CaSpr2 significantly reduced JA and JA-Ile accumulation, and led to a strong feeding preference of WFTs for CaSpr2-silenced plants. Furthermore, the adult lifespan, survival rate, female fecundity, oviposition rate, and population parameters of WFTs were significantly improved on CaSpr2-silenced plants. Spr2 functions as an essential component within the JA signaling pathway, thereby playing a critical role in conferring resistance to WFTs in cultivated pepper. These findings provide profound insights and practical implications for breeding thrips-resistant cultivars in non-model plants, through genetic manipulation of JA signaling, offering a promising avenue for sustainable agricultural pest management.