RESUMO
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.
Assuntos
Regulação da Expressão Gênica de Plantas , Repetições de Microssatélites , Psidium , Psidium/genética , Repetições de Microssatélites/genética , Repetições de Trinucleotídeos/genética , Perfilação da Expressão Gênica , Folhas de Planta/genética , Folhas de Planta/metabolismo , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismoRESUMO
Psidium guajava L., a fruit crop belonging to the Myrtaceae family, is highly valued for its nutritional and medicinal properties. The family exhibits a diverse chemical profile of essential oils and serves as a valuable resource due to its ecological interactions, adaptability, and dispersal capacity. The Myrtaceae family has been extensively studied for its terpenoids. Genetic studies have focused on foliar terpene yield in species from the Eucalypteae and Melaleucaceae tribes. To understand the evolutionary trends in guava breeding, this study predicted terpene synthase genes (TPS) from different cultivars. Through this analysis, 43 full-length TPS genes were identified, and approximately 77% of them exhibited relative expression in at least one of the five investigated plant tissues (root, leaf, bud, flower, and fruit) of two guava cultivars. We identified intra-species variation in the terpene profile and single nucleotide polymorphisms (SNPs) in twelve TPS genes, resulting in the clustering of 62 genotypes according to their essential oil chemotypes. The high concentration of sesquiterpenes is supported by the higher number of TPS-a genes and their expression. The expansion for TPS sub-families in P. guajava occurred after the expansion of other rosids species. Providing insight into the origin of structural diversification and expansion in each clade of the TPS gene family within Myrtaceae. This study can provide insights into the diversity of genes for specialized metabolites such as terpenes, and their regulation, which can lead to a diverse chemotype of essential oil in different tissues and genotypes. This suggests a mode of enzymatic evolution that could lead to high sesquiterpene production, act as a chemical defense and contribute to the adaptive capacity of this species to different habitats.