title: From model to crop: functional analysis of a STAY-GREEN gene in the model legume Medicago truncatula and effective use of the gene for alfalfa improvement.
abstract: Medicago truncatula has been developed into a model legume. Its close relative alfalfa (Medicago sativa) is the most widely grown forage legume crop in the United States. By screening a large population of M. truncatula mutants tagged with the transposable element of tobacco (Nicotiana tabacum) cell type1 (Tnt1), we identified a mutant line (NF2089) that maintained green leaves and showed green anthers, central carpels, mature pods, and seeds during senescence. Genetic and molecular analyses revealed that the mutation was caused by Tnt1 insertion in a STAY-GREEN (MtSGR) gene. Transcript profiling analysis of the mutant showed that loss of the MtSGR function affected the expression of a large number of genes involved in different biological processes. Further analyses revealed that SGR is implicated in nodule development and senescence. MtSGR expression was detected across all nodule developmental zones and was higher in the senescence zone. The number of young nodules on the mutant roots was higher than in the wild type. Expression levels of several nodule senescence markers were reduced in the sgr mutant. Based on the MtSGR sequence, an alfalfa SGR gene (MsSGR) was cloned, and transgenic alfalfa lines were produced by RNA interference. Silencing of MsSGR led to the production of stay-green transgenic alfalfa. This beneficial trait offers the opportunity to produce premium alfalfa hay with a more greenish appearance. In addition, most of the transgenic alfalfa lines retained more than 50% of chlorophylls during senescence and had increased crude protein content. This study illustrates the effective use of knowledge gained from a model system for the genetic improvement of an important commercial crop.
authors.affiliation: Forage Improvement Division, Samuel Roberts Noble Foundation, Ardmore, Oklahoma 73401, USA.
authors.forename: Chuanen
authors.initials: C
authors.lastname: Zhou
authors.forename: Lu
authors.initials: L
authors.lastname: Han
authors.forename: Catalina
authors.initials: C
authors.lastname: Pislariu
authors.forename: Jin
authors.initials: J
authors.lastname: Nakashima
authors.forename: Chunxiang
authors.initials: C
authors.lastname: Fu
authors.forename: Qingzhen
authors.initials: Q
authors.lastname: Jiang
authors.forename: Li
authors.initials: L
authors.lastname: Quan
authors.forename: Elison B
authors.initials: EB
authors.lastname: Blancaflor
authors.forename: Yuhong
authors.initials: Y
authors.lastname: Tang
authors.forename: Joseph H
authors.initials: JH
authors.lastname: Bouton
authors.forename: Michael
authors.initials: M
authors.lastname: Udvardi
authors.forename: Guangmin
authors.initials: G
authors.lastname: Xia
authors.forename: Zeng-Yu
authors.initials: ZY
authors.lastname: Wang
mesh_terms: D000383:Agriculture / Q000379:methods*; D002734:Chlorophyll / Q000378:metabolism; D002736:Chloroplasts / Q000378:metabolism / Q000648:ultrastructure; D003001:Cloning, Molecular; D018556:Crops, Agricultural / Q000235:genetics*; D003624:Darkness; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant / Q000235:genetics*; D000455:Medicago sativa / Q000235:genetics* / Q000502:physiology; D046913:Medicago truncatula / Q000235:genetics* / Q000254:growth & development / Q000648:ultrastructure; D008954:Models, Biological; D009154:Mutation / Q000235:genetics; D010641:Phenotype; D018515:Plant Leaves / Q000254:growth & development / Q000648:ultrastructure; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified; D034622:RNA Interference; D053204:Root Nodules, Plant / Q000254:growth & development / Q000378:metabolism
chemical_list: D010940:Plant Proteins; D002734:Chlorophyll