Relação entre a expressão gênica e a dormência em sementes de amendoim

Abstract

Peanut (Arachis hypogaea) is an important oleaginous for the food sector due to the high nutritional value of grains and oil. The crop is grown with upright and runner cultivars that attend the food and oil markets. The runner genotypes are high yield, but the seeds often have high level of dormancy, whose process is triggered due to some metabolic steps that prevent the synthesis of proteins and transport of reserves to the embryo. The regulation involves several genes that act by activating or repressing the action of endogenous hormones, such as ARP (auxin repressor protein) and DMR1 (Dormancy-associated gene 1) family genes that are directly involved with auxin activity in some species. Both regulate the auxin synthesis, whose hormone is responsible for plant development and growth. The NCED (9-cis-epoxy-carotenoid dioxygenase) is responsible for regulating of ABA synthesis, which is also related to plant growth. This work was aimed to investigate the involvement of the expression of genes associated with dormancy in peanut seeds. The assays were carried out by using genotypes previously phenotyped for dormancy traits, adopting physiological and molecular tests. In the physiological assays, the following descriptors were used: percentage of germination, length of seedlings and time in days that the seeds took to germinate, evaluated in three replicates for each genotype. The molecular assays consisted of semiquantitative (RT-PCR) and quantitative (RT- qPCR) procedures. We found high expression of NCED and ARP in embryos of IAC Caiapó and LGoPE-06, both runner genotypes, confirming the relationship of genes with seed dormancy. The expression of DMR1 was higher in the cotyledon from upright genotypes, L7 Bege and BR 1. NCED is a reliable molecular marker to assist in the identification of dormancy in peanut genotypes.