title: Chloroplast-like organelles were found in enucleate sieve elements of transgenic plants overexpressing a proteinase inhibitor.
abstract: SaPIN2a, a plant proteinase inhibitor from nightshade (Solanum americanum), was located to the enucleate sieve elements (SEs) of phloem. The expressed SaPIN2a in transgenic lettuce showed inhibition of plant endogenous trypsin- and chymotrypsin-like activities, suggesting that SaPIN2a can regulate proteolysis in plant cells. To further investigate the physiological role of SaPIN2a, we produced transgenic nightshade and lettuce plants overexpressing SaPIN2a from the cauliflower mosaic virus (CaMV) 35S promoter using Agrobacterium-mediated transformation. Overexpression of SaPIN2a in transgenic plants was demonstrated by northern blot and western blot analysis. SaPIN2a-overexpressing transgenic nightshade plants showed significantly lower height than wild-type plants. Transmission electron microscopy analysis showed that chloroplast-like organelles with thylakoids, which are not present in enucleate SEs of wild-type plants, were present in the enucleate SEs of SaPIN2a-overexpressing transgenic plants. This finding is discussed in terms of the possible role played by SaPIN2a in the regulation of proteolysis in SEs.
authors.affiliation: State Key Laboratory of Biocontrol and Key Laboratory of Gene Engineering of the Ministry of Education, School of Life Sciences, Sun Yat-sen University, Guangzhou 510275, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Xie
authors.forename: Xue-Zhi
authors.initials: XZ
authors.lastname: Ouyang
authors.forename: Kuai-Fei
authors.initials: KF
authors.lastname: Xia
authors.forename: Yu-Feng
authors.initials: YF
authors.lastname: Huang
authors.forename: Wen-Bi
authors.initials: WB
authors.lastname: Pan
authors.forename: Ying-Peng
authors.initials: YP
authors.lastname: Cai
authors.forename: Xinping
authors.initials: X
authors.lastname: Xu
authors.forename: Baojian
authors.initials: B
authors.lastname: Li
authors.forename: Zeng-Fu
authors.initials: ZF
authors.lastname: Xu
mesh_terms: D017796:Caulimovirus / Q000235:genetics; D002736:Chloroplasts / Q000648:ultrastructure*; D018545:Lactuca / Q000235:genetics* / Q000648:ultrastructure*; D046529:Microscopy, Electron, Transmission; D015388:Organelles / Q000648:ultrastructure; D052585:Phloem / Q000737:chemistry / Q000648:ultrastructure; D030821:Plants, Genetically Modified / Q000235:genetics* / Q000648:ultrastructure*; D011401:Promoter Regions, Genetic; D012231:Rhizobium / Q000235:genetics; D015842:Serine Proteinase Inhibitors / Q000032:analysis / Q000235:genetics / Q000502:physiology*; D032322:Solanum / Q000235:genetics; D020524:Thylakoids / Q000648:ultrastructure
chemical_list: D015842:Serine Proteinase Inhibitors