Poliploidia sintética em Lippia alba (Mill.) N.E. Brown: indução e efeitos da duplicação do genoma

Abstract

Polyploidy is an important evolutionary mechanism in plants, being associated with diversification, adaptation, and phenotypic innovation. In addition to its evolutionary role, synthetic polyploidization has been widely used as a tool to investigate the immediate effects of increased gene dosage on different levels of biological organization. In this context, this work aimed to expand the knowledge of the effects of chromosome duplication in Lippia alba, a medicinal species that constitutes a natural autopolyploid complex, through the induction, characterization, and molecular analysis of synthetic polyploids. Initially, polyploids were induced from diploid and triploid accessions using colchicine and trifluralin. Induction efficiency, the influence of nodal position, genetic stability, morphological, anatomical, and physiological traits, essential oil composition, and the expression of genes involved in terpene biosynthesis were evaluated. Subsequently, transcriptional changes induced by chromosome duplication were investigated using RNA-seq, including de novo transcriptome assembly, functional annotation, differential gene expression analysis, Gene Ontology (GO)-based functional enrichment analysis, and RT-qPCR validation. Longer exposure to antimitotic agents increased polyploid induction frequency but reduced explant survival, whereas nodal position significantly influenced induction efficiency. Synthetic polyploids exhibited changes in vegetative growth, stomatal anatomy, biomass accumulation, and the expression of terpene biosynthesis-related genes, although they remained phenotypically more similar to their respective parental plants. Transcriptome analysis identified 2,169 differentially expressed genes and 66 significantly enriched GO terms, mainly associated with chromatin organization, transcriptional regulation, cell division, microtubule dynamics, cell wall remodeling, and stress responses. RT-qPCR validation corroborated the expression patterns observed in the RNA-seq analysis. Overall, the results demonstrate that synthetic polyploidization promotes extensive morphophysiological and molecular changes during the establishment of new cytotypes and further demonstrate that the genetic background plays a determinant role in the phenotypic characteristics and in the magnitude of the responses to polyploidization.