title: Transcriptome analysis reveals the effects of sugar metabolism and auxin and cytokinin signaling pathways on root growth and development of grafted apple.
abstract: BACKGROUND
  The root architecture of grafted apple (Malus spp.) is affected by various characteristics of the scions. To provide information on the molecular mechanisms underlying this influence, we examined root transcriptomes of M. robusta rootstock grafted with scions of wild-type (WT) apple (M. spectabilis) and a more-branching (MB) mutant at the branching stage.
  
  
  RESULTS
  The growth rate of rootstock grafted MB was repressed significantly, especially the primary root length and diameter, and root weight. Biological function categories of differentially expressed genes were significantly enriched in processes associated with hormone signal transduction and intracellular activity, with processes related to the cell cycle especially down-regulated. Roots of rootstock grafted with MB scions displayed elevated auxin and cytokinin contents and reduced expression of MrPIN1, MrARF, MrAHP, most MrCRE1 genes, and cell growth-related genes MrGH3, MrSAUR and MrTCH4. Although auxin accumulation and transcription of MrPIN3, MrALF1 and MrALF4 tended to induce lateral root formation in MB-grafted rootstock, the number of lateral roots was not significantly changed. Sucrose, fructose and glucose contents were not decreased in MB-grafted roots compared with those bearing WT scions, but glycolysis and tricarboxylic acid cycle metabolic activities were repressed. Root resistance and nitrogen metabolism were reduced in MB-grafted roots as well.
  
  
  CONCLUSIONS
  Our findings suggest that root growth and development of rootstock are mainly influenced by sugar metabolism and auxin and cytokinin signaling pathways. This study provides a basis that the characteristics of scions are related to root growth and development, resistance and activity of rootstocks.
authors.affiliation: College of Horticulture, Northwest A & F University, Yangling, Shaanxi, 712100, China. guofangli@nwsuaf.edu.cn.
authors.forename: Guofang
authors.initials: G
authors.lastname: Li
authors.affiliation: College of Horticulture, Northwest A & F University, Yangling, Shaanxi, 712100, China. mj25@qq.com.
authors.forename: Juanjuan
authors.initials: J
authors.lastname: Ma
authors.affiliation: College of Horticulture, Northwest A & F University, Yangling, Shaanxi, 712100, China. tm010411@163.com.
authors.forename: Ming
authors.initials: M
authors.lastname: Tan
authors.affiliation: College of Horticulture, Northwest A & F University, Yangling, Shaanxi, 712100, China. mjp588@163.com.
authors.forename: Jiangping
authors.initials: J
authors.lastname: Mao
authors.affiliation: College of Horticulture, Northwest A & F University, Yangling, Shaanxi, 712100, China. anna_luck@163.com.
authors.forename: Na
authors.initials: N
authors.lastname: An
authors.affiliation: Institute of agricultural science, Qingdao, Shandong, 266000, China. guanglisha@126.com.
authors.forename: Guangli
authors.initials: G
authors.lastname: Sha
authors.affiliation: College of Horticulture, Northwest A & F University, Yangling, Shaanxi, 712100, China. afant@nwsuaf.edu.cn.
authors.forename: Dong
authors.initials: D
authors.lastname: Zhang
authors.affiliation: College of Horticulture, Northwest A & F University, Yangling, Shaanxi, 712100, China. cpzhao403@163.com.
authors.forename: Caiping
authors.initials: C
authors.lastname: Zhao
authors.affiliation: College of Horticulture, Northwest A & F University, Yangling, Shaanxi, 712100, China. hanmy@nwsuaf.edu.cn.
authors.forename: Mingyu
authors.initials: M
authors.lastname: Han
mesh_terms: D050260:Carbohydrate Metabolism; D003583:Cytokinins / Q000378:metabolism*; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D007210:Indoleacetic Acids / Q000378:metabolism*; D027845:Malus / Q000235:genetics / Q000378:metabolism*; D010641:Phenotype; D018517:Plant Roots / Q000254:growth & development; D018749:RNA, Plant / Q000235:genetics; D017423:Sequence Analysis, RNA; D015398:Signal Transduction; D059467:Transcriptome
chemical_list: D003583:Cytokinins; D007210:Indoleacetic Acids; D018749:RNA, Plant