title: Analysis by virus induced gene silencing of the expression of two proline biosynthetic pathway genes in Nicotiana benthamiana under stress conditions.
abstract: Proline accumulation is responsible for stress adaptation in many plants. To distinguish the involvement of two proline synthetic pathways, the virus induced gene silencing (VIGS) system that silenced the expression of genes encoding Δ(1)-pyrroline-5-carboxylate synthetase (P5CS; EC:1.5.1.12) and ornithine-δ-aminotransferase (OAT; EC 2.6.1.13) was performed, separately or concomitantly, in four-week-old Nicotiana benthamiana. Leaf discs of VIGS-treated tobacco were subjected to the treatment of drought, abscisic acid (ABA), or polyethylene glycol (PEG). The treated leaf discs were then collected for the determination of mRNA, chlorophyll, proline and polyamine level. Under drought stress or PEG treatment, most proline accumulation was inhibited in P5CS-silenced plants and only a small portion was inhibited in OAT-silenced plants under drought stress and no inhibition was observed under PEG treatment. Under ABA treatment, proline accumulation was inhibited completely in P5CS-silenced plants but unaffected in OAT-silenced plants. The degradation of chlorophyll was enhanced in P5CS-silenced plants but retarded in OAT-silenced plants under PEG treatment. Under ABA treatment, the degradation of chlorophyll was unaffected in both P5CS-silenced and OAT-silenced plants. The increase of polyamine level was unaffected in P5CS-silenced plants but increased in OAT-silenced plants under PEG treatment. Under ABA treatment, the increase of polyamine level was unaffected in P5CS-silenced plants but the polyamine level was increased later in OAT-silenced plants. Therefore, P5CS plays a major role in proline accumulation under drought, PEG, or ABA treatment, while OAT plays a minor role in drought or PEG treatment and does not participate in ABA treatment. OAT appears to have a close relationship with the regulation of polyamine levels in PEG and ABA treatments.
authors.affiliation: Department of Agronomy, National Chung Hsing University, Taichung 402, Taiwan.
authors.forename: Hsin-Mei
authors.initials: HM
authors.lastname: Ku
authors.forename: Chi-Chieh
authors.initials: CC
authors.lastname: Hu
authors.forename: Hui-Ju
authors.initials: HJ
authors.lastname: Chang
authors.forename: Yu-Tsung
authors.initials: YT
authors.lastname: Lin
authors.forename: Fuh-Jyh
authors.initials: FJ
authors.lastname: Jan
authors.forename: Chien-Teh
authors.initials: CT
authors.lastname: Chen
mesh_terms: D050842:1-Pyrroline-5-Carboxylate Dehydrogenase / Q000235:genetics / Q000378:metabolism; D000040:Abscisic Acid / Q000494:pharmacology; D053898:Biosynthetic Pathways; D002734:Chlorophyll / Q000378:metabolism; D003001:Cloning, Molecular; D003681:Dehydration; D055864:Droughts; D018506:Gene Expression Regulation, Plant; D020868:Gene Silencing; D017343:Genes, Plant; D005822:Genetic Vectors / Q000235:genetics / Q000378:metabolism; D050698:Glutamate-5-Semialdehyde Dehydrogenase / Q000235:genetics / Q000378:metabolism; D009097:Multienzyme Complexes / Q000235:genetics / Q000378:metabolism; D009953:Ornithine-Oxo-Acid Transaminase / Q000235:genetics / Q000378:metabolism; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000235:genetics / Q000378:metabolism; D018515:Plant Leaves / Q000187:drug effects / Q000235:genetics / Q000502:physiology / Q000821:virology; D011073:Polyamines / Q000378:metabolism; D011092:Polyethylene Glycols / Q000494:pharmacology; D011392:Proline / Q000096:biosynthesis* / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis; D013312:Stress, Physiological; D014026:Nicotiana / Q000187:drug effects / Q000201:enzymology / Q000235:genetics* / Q000821:virology; D014027:Tobacco Mosaic Virus / Q000235:genetics / Q000378:metabolism
chemical_list: D009097:Multienzyme Complexes; D011073:Polyamines; D012333:RNA, Messenger; D002734:Chlorophyll; D011092:Polyethylene Glycols; D000040:Abscisic Acid; D011392:Proline; D050698:Glutamate-5-Semialdehyde Dehydrogenase; D050842:1-Pyrroline-5-Carboxylate Dehydrogenase; D009953:Ornithine-Oxo-Acid Transaminase; D017853:Phosphotransferases (Alcohol Group Acceptor)