Differential expression of gibberellin-related genes in wild type and dwarf mutant of Poa pratensis implied their roles in regulating plant height

Gibberellins (GA) are important hormones in the regulation of plant growth and development, especially plant dwarfism. In the present study, the leaf length and active gibberellin content of a dwarf mutant were lower than that of Kentucky bluegrass (Poa pratensis L.) wild type, and the plant height of the dwarf mutant increased following the application of GA(3). To gain insights into the GA metabolism pathway in turfgrass and the role of GA-related genes in the dwarf phenotype, five GA-related genes in P. pratensis, namely PpKS, PpKO, PpGA20ox1, PpGA3ox1, and PpGA2ox5, were isolated and identified. According to expression analysis, the expression levels of PpKS were lower in the dwarf mutant than in the wild type, whereas the transcript abundances of PpGA20ox1 and PpGA2ox5 were raised in dwarf mutant. Further evaluation of the expression profiles of these genes in response to GA(3) showed that the studied genes were differentially regulated after exogenous treatment. Furthermore, it was found that PpGA2ox5-overexpressing transgenic lines produced the phenotypes of dwarfism and dark green blades, whereas PpGA20ox1 overexpression in Arabidopsis had the opposite effect. Through the result of the diverse expression patterns of GA genes and functional study of PpGA2ox5 and PpGA20ox1, it is indicated that the genes involved in the metabolism of GA are important for regulating plant height and speculated that PpGA2ox5 could be the breeding target that used to cultivate dwarf varieties of Kentucky bluegrass.