# Effects of trimer repeats on Psidium guajava L. gene expression and prospection of functional microsatellite markers

## TL;DR

This study explores how trinucleotide repeats affect gene expression in guava plants and identifies potential genetic markers for use in related species.

## Contribution

The study is among the first to investigate the impact of trinucleotide repeats on gene expression in plants, specifically Psidium guajava L.

## Key findings

- TR-containing genes are involved in cellular structures, stress response, and resistance.
- Differential gene expression was observed between two guava cultivars, with many down-regulated genes in one cultivar.
- A set of 20 genes with TRs was identified as potential phenotypic markers for Psidium guajava and related species.

## Abstract

Most research on trinucleotide repeats (TRs) focuses on human diseases, with few on the impact of TR expansions on plant gene expression. This work investigates TRs' effect on global gene expression in Psidium guajava L., a plant species with widespread distribution and significant relevance in the food, pharmacology, and economics sectors. We analyzed TR-containing coding sequences in 1,107 transcripts from 2,256 genes across root, shoot, young leaf, old leaf, and flower bud tissues of the Brazilian guava cultivars Cortibel RM and Paluma. Structural analysis revealed TR sequences with small repeat numbers (5–9) starting with cytosine or guanine or containing these bases. Functional annotation indicated TR-containing genes' involvement in cellular structures and processes (especially cell membranes and signal recognition), stress response, and resistance. Gene expression analysis showed significant variation, with a subset of highly expressed genes in both cultivars. Differential expression highlighted numerous down-regulated genes in Cortibel RM tissues, but not in Paluma, suggesting interplay between tissues and cultivars. Among 72 differentially expressed genes with TRs, 24 form miRNAs, 13 encode transcription factors, and 11 are associated with transposable elements. In addition, a set of 20 SSR-annotated, transcribed, and differentially expressed genes with TRs was selected as phenotypic markers for Psidium guajava and, potentially for closely related species as well.