Caracterização in silico de transportadores de fósforo e desempenho de cultivares de Megathyrsus maximus em diferentes níveis de fósforo

Abstract

Forage grasses are the main source of food for ruminant animals, however, phosphorus (P) deficiency in tropical soils negatively affects pasture productivity and quality. Plants have a complex phosphorus acquisition and distribution system that involves different cellular transporters. However, genes related to P transport in Panicum spp. are little studied. The objective of this work was to characterize in silico the vacuolar H+-pyrophosphatase (VHP) and phosphate transporters (PHT1 and PHO1) genes in Panicum spp. and, to evaluate the transcriptional profile of P transporters and the performance of two cultivars of Megathyrsus maximus (syn. Panicum maximum), under P levels. The gene sequences described in Arabidopsis thaliana and Oryza sativa were used to identify homologous sequences in the species Panicum hallii and Panicum virgatum available in Phytozome v 13. The experiment was carried out in a greenhouse, the seedlings of two cultivars (Mombaça and Aruana) of M. maximus were submitted to low and adequate P (0.05 mM and 1 mM of KH2PO4). Productive parameters and forage quality were evaluated after 21 days of growth in treatments with P levels. We identified 8, 12 and 3 genes in P. hallii and 14, 23 and 6 genes in P. virgatum, belonging to the VHP families, PHT1 and PHO1, respectively. Based on the phylogenetic comparison between Panicum spp species, primers were designed for four genes MmVHP1, MmPHT1, MmPHO1b and MmPHO1c, whose expression was analyzed in leaves and roots of M. maximus. The cultivars showed lower expression of the MmVHP1 gene and higher expression of the MmPHT1 and MmPHO1b genes in the leaves, in response to low P. In the roots, the expression of the MmPHT1 gene was upregulated. MmPHO1c showed low expression and was not induced by the treatments. The low availability of P reduced the number of leaves, tillering, shoot biomass and nutritional value of both cultivars, however, the plants showed greater growth of smaller diameter roots. The nutritional quality of cv. Mombaça was affected by an increase in lignin and a decrease in hemicellulose at low P. The results obtained in this work reinforce the potential of using a Panicum spp. for studies in related species with a unsequenced genome, such as M. maximus, for the understanding of acquisition strategies and internal use of P by plants under conditions of low P availability.