Endo-β-Mananase e α-galactosidase e suas relações com a tolerância à termoinibição em sementes de alface

Abstract

Temperature strongly influences the germination of lettuce seeds (Lactuca sativa L.) due to the thermoinhibition effect. The aim of this study was to determine the enzymatic activity and gene expression of different enzymes associated with the thermoinhibition effect of lettuce seeds. Seeds of the cultivars Everglades (tolerant to thermoinhibition) and Verônica (sensitive to thermoinhibition), the reciprocal hybrids, originated from the cross between the two cultivars and the F2 generation were used. The seeds were submitted to germination tests, first germination count, germination speed index (VIG) and enzymatic tests (Catalase, superoxide dismutase, ascorbate peroxidase and endo-β-mannanase). Subsequently, the expression of genes related to endo-β-mannanase and α-galactosidase enzymes was evaluated by RTq-PCR. Regarding the physiological tests, the Everglades cultivar, as well as its hybrids, were less thermoinhibited than the other treatments. The activities of the enzymes superoxide dismutase and endo-β-mannanase showed a direct and more expressive relationship with the alterations in the physiological parameters of thermotolerance. Regarding gene expression, there was variation in transcripts that express endo-β-mannanase and α-galactosidase between the treatments evaluated. However, endo-β-mannanase followed the trend of the thermoinhibition trait and may be associated with this trait in Lactuca sativa seeds. Therefore, it is concluded that endo-β-mannanase is a promising enzymatic and genetic marker associated with thermotolerance and is an important tool in the selection of cultivars in lettuce breeding programs.