title: Senescence-inducible expression of isopentenyl transferase extends leaf life, increases drought stress resistance and alters cytokinin metabolism in cassava.
abstract: Cassava (Manihot esculenta Crantz) sheds its leaves during growth, especially within the tropical dry season. With the production of SAG12-IPT transgenic cassava we want to test the level of leaf retention and altered cytokinin metabolism of transgenic plants via the autoregulatory senescence inhibition system. After confirmation of transgene expression by molecular analysis and phenotype examination in greenhouse plants, two transgenic plant lines, 529-28 and 529-48, were chosen for further investigation. Detached mature leaves of 529-28 plants retained high levels of chlorophyll compared with wild-type leaves after dark-induced senescence treatment. Line 529-28 showed significant drought tolerance as indicated by stay-green capacity after drought stress treatment. Field experiments proved that leaf senescence syndrome was significantly delayed in 529-28 plants in comparison with wild-type and 529-48 plants. Physiological and agronomical characterizations of these plants also revealed that the induced expression of IPT had effects on photosynthesis, sugar allocation and nitrogen partitioning. Importantly, the 529-28 plants accumulated a high level of trans-zeatin-type cytokinins particularly of corresponding storage O-glucosides to maintain cytokinin homeostasis. Our study proves the feasibility of prolonging the leaf life of woody cassava and also sheds light on the control of cytokinin homeostasis in cassava leaves.
authors.affiliation: Shanghai Center for Cassava Biotechnology, National Laboratory of Plant Molecular Genetics, Institute of Plant Physiology & Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China.
authors.forename: Peng
authors.initials: P
authors.lastname: Zhang
authors.forename: Wen-Quan
authors.initials: WQ
authors.lastname: Wang
authors.forename: Gen-Liang
authors.initials: GL
authors.lastname: Zhang
authors.forename: Miroslav
authors.initials: M
authors.lastname: Kaminek
authors.forename: Petre
authors.initials: P
authors.lastname: Dobrev
authors.forename: Jia
authors.initials: J
authors.lastname: Xu
authors.forename: Wilhelm
authors.initials: W
authors.lastname: Gruissem
mesh_terms: D019883:Alkyl and Aryl Transferases / Q000235:genetics / Q000378:metabolism*; D016922:Cellular Senescence / Q000235:genetics / Q000502:physiology*; D002734:Chlorophyll / Q000378:metabolism; D003583:Cytokinins / Q000378:metabolism*; D003681:Dehydration; D055864:Droughts; D018506:Gene Expression Regulation, Plant / Q000235:genetics / Q000502:physiology; D002365:Manihot / Q000201:enzymology* / Q000235:genetics; D018515:Plant Leaves / Q000201:enzymology* / Q000235:genetics; D030821:Plants, Genetically Modified / Q000201:enzymology / Q000235:genetics / Q000378:metabolism
chemical_list: D003583:Cytokinins; D002734:Chlorophyll; D019883:Alkyl and Aryl Transferases; C024274:adenylate isopentenyltransferase