title: Functional characterization of the apple MhGAI1 gene through ectopic expression and grafting experiments in tomatoes.
abstract: DELLA proteins are essential components of GA signal transduction. MhGAI1 was isolated from the tea crabapple (Malus hupehensis Redh. var. pingyiensis), and it was found to encode a DELLA protein. Mhgai1 is a GA-insensitive allele that was artificially generated via a bridge-PCR approach. Ectopic expression of Mhgai1 reduced plant stature, decreased spontaneous fruit-set-ratio and enhanced drought-tolerance in transgenic tomatoes. In addition, we examined the long-distance movement of Mhgai1 mRNAs by grafting experiments and SqRT-PCR analysis. It was found that the wild-type scions accumulated Mhgai1 transcripts trafficked from the transgenic rootstocks and therefore exhibited dwarf phenotypes. Furthermore, transgenic tomato plants produced more soluble solids, sugars and organic acids compared to wild-type tomatoes, suggesting an involvement of GA signaling in the regulation of fruit quality. Despite noticeable accumulation in the leaves and stems of WT scions, Mhgai1 transcripts were undetectable in flowers and fruit. Therefore, fruit quality was less influenced by the grafting of WT scions onto transgenic rootstocks than they were by the ectopic expression of Mhgai1 in transgenic rootstocks. Taken together, MhGAI1, which functions as a repressor in the GA signaling pathway, and its GA-insensitive allele, Mhgai1, could turn out to be useful targets for the genetic improvement of dwarfing rootstocks in apples.
authors.affiliation: State Key Laboratory of Crop Biology, National Research Center for Apple Engineering and Technology, College of Horticulture Science and Engineering, Shandong Agricultural University, Tai-An, Shandong 271018, China.
authors.forename: Shuang-Shuang
authors.initials: SS
authors.lastname: Wang
authors.forename: Ze-Zhou
authors.initials: ZZ
authors.lastname: Liu
authors.forename: Chao
authors.initials: C
authors.lastname: Sun
authors.forename: Qing-Hua
authors.initials: QH
authors.lastname: Shi
authors.forename: Yu-Xin
authors.initials: YX
authors.lastname: Yao
authors.forename: Chun-Xiang
authors.initials: CX
authors.lastname: You
authors.forename: Yu-Jin
authors.initials: YJ
authors.lastname: Hao
mesh_terms: D000595:Amino Acid Sequence; D002681:China; D005638:Fruit / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D005875:Gibberellins / Q000378:metabolism; D018551:Solanum lycopersicum / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D027845:Malus / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D008969:Molecular Sequence Data; D010641:Phenotype; D010937:Plant Growth Regulators / Q000378:metabolism; D010940:Plant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics*; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism; D014170:Transformation, Genetic
chemical_list: D005875:Gibberellins; D010937:Plant Growth Regulators; D010940:Plant Proteins; C007842:gibberellic acid