Expressão de genes relacionados à apomixa ao longo do desenvolvimento reprodutivo em Urochloa decumbens e Urochloa ruziziensis (Poaceae)

Abstract

Urochloa decumbens is a grass with predominance of apomictic reproduction that presents elevated importance as forage in tropical countries. However, studies with candidate genes to the apomixis control are still limited. Urochloa ruziziensis is genetically related to U. decumbens, but reproduces sexually. The aim of the present study was to describe the developmental stages of the embryonic sac (megasporogenesis and megagametogenesis) associated with morphometric traits of the spikelets and to characterize the temporal space expression of BbrizRan, BbrizStil and BbrizAGL6 gene transcripts in U. ruziziensis cv. Kennedy (diploid, sexual) and U. decumbens cv. Basilisk (tetraploid, apomictic). Initially, the length and width of young spikelets were evaluated and anatomical cuts were performed. Expression analysis (using RT qPCR) was performed for the genes BbrizSti1, BbrizRan and BbrizAGL6, using spikelets during the megasporogenesis and megagametogenesis stages. The results showed that the spikelet length can be used as a reliable morphological marker to discriminate both stages in U. ruziziensis and U. decumbens. The megaspore mother cell was observed in megasporogenesis in both species. The embryonic sacs observed were classified as Polygonum type in U. ruziziensis and Panicum type in U. decumbens. The RT qPCR analysis indicated that the BbrizRan, BbrizStil and BbrizAGL6 genes are involved in the reproductive development of both species. The BbrizStil gene presents higher expression levels in the apomictic plant during megasporogenesis, which indicates the involvement of this specific gene during the early stage of differentiation of U. decumbens. The BbrizRan gene acts in the early and final stages of apomictic differentiation of U. decumbens. The information obtained in this study may be useful for future studies that aim to better understand the apomixis and sexual reproduction in Urochloa.