title: Cytokinin-mediated source/sink modifications improve drought tolerance and increase grain yield in rice under water-stress.
abstract: Drought is the major environmental factor limiting crop productivity worldwide. We hypothesized that it is possible to enhance drought tolerance by delaying stress-induced senescence through the stress-induced synthesis of cytokinins in crop-plants. We generated transgenic rice (Oryza sativa) plants expressing an isopentenyltransferase (IPT) gene driven by P(SARK) , a stress- and maturation-induced promoter. Plants were tested for drought tolerance at two yield-sensitive developmental stages: pre- and post-anthesis. Under both treatments, the transgenic rice plants exhibited delayed response to stress with significantly higher grain yield (GY) when compared to wild-type plants. Gene expression analysis revealed a significant shift in expression of hormone-associated genes in the transgenic plants. During water-stress (WS), P(SARK)::IPT plants displayed increased expression of brassinosteroid-related genes and repression of jasmonate-related genes. Changes in hormone homeostasis were associated with resource(s) mobilization during stress. The transgenic plants displayed differential expression of genes encoding enzymes associated with hormone synthesis and hormone-regulated pathways. These changes and associated hormonal crosstalk resulted in the modification of source/sink relationships and a stronger sink capacity of the P(SARK)::IPT plants during WS. As a result, the transgenic plants had higher GY with improved quality (nutrients and starch content).
authors.affiliation: Department of Plant Sciences, University of California, Davis, CA, USA.
authors.forename: Zvi
authors.initials: Z
authors.lastname: Peleg
authors.forename: Maria
authors.initials: M
authors.lastname: Reguera
authors.forename: Ellen
authors.initials: E
authors.lastname: Tumimbang
authors.forename: Harkamal
authors.initials: H
authors.lastname: Walia
authors.forename: Eduardo
authors.initials: E
authors.lastname: Blumwald
mesh_terms: D019883:Alkyl and Aryl Transferases / Q000235:genetics / Q000378:metabolism*; D018533:Biomass; D002734:Chlorophyll / Q000378:metabolism; D003583:Cytokinins / Q000096:biosynthesis*; D003681:Dehydration; D055864:Droughts; D002523:Edible Grain / Q000737:chemistry / Q000254:growth & development* / Q000378:metabolism; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D006706:Homeostasis / Q000235:genetics; D012275:Oryza / Q000737:chemistry / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D010937:Plant Growth Regulators / Q000235:genetics / Q000378:metabolism; D018515:Plant Leaves / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000737:chemistry / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D011401:Promoter Regions, Genetic; D036226:Seedlings / Q000235:genetics / Q000254:growth & development / Q000502:physiology; D013213:Starch / Q000378:metabolism; D013395:Sucrose / Q000378:metabolism; D013997:Time Factors
chemical_list: D003583:Cytokinins; D010937:Plant Growth Regulators; D010940:Plant Proteins; D002734:Chlorophyll; D013395:Sucrose; D013213:Starch; D019883:Alkyl and Aryl Transferases; C024274:adenylate isopentenyltransferase