Cloning and Functional Analysis of Dwarf Gene Mini Plant 1 ( MNP1 ) in Medicago truncatula .

Plant height is a vital agronomic trait that greatly determines crop yields because of the close relationship between plant height and lodging resistance. Legumes play a unique role in the worldwide agriculture; however, little attention has been given to the molecular basis of their height. Here, we characterized the first dwarf mutantmini plant 1(mnp1) of the model legume plantMedicago truncatula. Our study found that both cell length and the cell number of internodes were reduced in amnp1mutant. Using the forward genetic screening and subsequent whole-genome resequencing approach, we cloned theMNP1gene and found that it encodes a putative copalyl diphosphate synthase (CPS) implicated in the first step of gibberellin (GA) biosynthesis. MNP1 was highly homologous toPisum sativumLS. The subcellular localization showed that MNP1 was located in the chloroplast. Further analysis indicated that GA(3)could significantly restore the plant height ofmnp1-1, and expression ofMNP1in acps1mutant ofArabidopsispartially rescued its mini-plant phenotype, indicating the conservation function of MNP1 in GA biosynthesis. Our results provide valuable information for understanding the genetic regulation of plant height inM. truncatula.