Respostas morfofisiológicas e expressão gênica do complexo poliploide Lippia alba sob condições de estresse

Abstract

Lippia alba (Mill) N.E. Brown, is a medicinal species whose composition of its essential oil is associated with ploidal levels (diploid, triploid and tetraploid). Polyploidy and environmental variations can lead to significant changes in the metabolic pathway. Due to the medicinal and economic importance of the species, investigating responses related to different stresses, it is important to understand the effect of polyploidy and modulate the production of compounds of interest. Thus, the objective of this work was to evaluate the effect of abiotic stresses on growth, physiology, essential oil production and on the expression of genes related to monoterpene pathway, in diploid, triploid and tetraploid accessions of L. alba cultivated for 40 days in vitro. Additionally, candidate reference genes in L. alba diploids were evaluated for different stress conditions. Thus, the three ploidal levels were cultivated in vitro, with the addition of 60 mM NaCl to induce salt stress; 1% PEG-4000 for water stress; 10 μM ABA for abscisic acid stress; 10 μM AS for salicylic acid stress; subjected to 4ºC to induce thermal stress and mechanical wounding stress. Six candidate reference genes were evaluated under the six stresses and analyzes of growth variables were performed; biochemical and physiological; gene expression related to monoterpene biosynthesis and microextraction of essential oil. Stresses were able to modulate morphophysiology, gene expression and essential oil content. The salt and water stress caused the biggest changes. Polyploid accessions showed, in general, greater growth and metabolic tolerance under stress, when compared to diploid accession. As a result of the evaluation of the reference genes, the NADH gene was the least variable under most stresses, except water stress, whose TUB gene was the most recommended. The results, taken together, demonstrated that abiotic stresses are capable of influencing morphophysiology and gene expression, as well as modulating the production of essential oils in Lippia alba, providing input for future breeding and species use strategies.