ABSTRACT
Plant lipoxygenases (LOXs) are a functionally diverse class of dioxygenases implicated in physiological processes such as growth, senescence, and stress-related responses. LOXs incorporate oxygen into their fatty acid substrates and produce hydroperoxide fatty acids that are precursors of jasmonic acid and related compounds. Here, we report the involvement of the tuber-associated LOXs, designated the Lox1 class, in the control of tuber growth. RNA hybridization analysis showed that the accumulation of Lox1 class transcripts was restricted to developing tubers, stolons, and roots and that mRNA accumulation correlated positively with tuber initiation and growth. In situ hybridization showed that Lox1 class transcripts accumulated in the apical and subapical regions of the newly formed tuber, specifically in the vascular tissue of the perimedullary region, the site of the most active cell growth during tuber enlargement. Suppression mutants produced by expressing antisense coding sequence of a specific tuber LOX, designated POTLX-1, exhibited a significant reduction in LOX activity in stolons and tubers. The suppression of LOX activity correlated with reduced tuber yield, decreased average tuber size, and a disruption of tuber formation. Our results indicate that the pathway initiated by the expression of the Lox1 class genes of potato is involved in the regulation of tuber enlargement.
Subject(s)
Lipoxygenase/biosynthesis , Solanum tuberosum/enzymology , Solanum tuberosum/growth & development , Cell Division , Gene Expression Regulation, Enzymologic , Gene Expression Regulation, Plant , Isoenzymes/biosynthesis , Isoenzymes/drug effects , Isoenzymes/genetics , Lipid Peroxides/biosynthesis , Lipid Peroxides/genetics , Lipoxygenase/drug effects , Lipoxygenase/genetics , Phylogeny , Plant Shoots/cytology , Plant Shoots/enzymology , Plant Shoots/genetics , Plant Shoots/growth & development , Plants, Genetically Modified , RNA, Antisense/metabolism , RNA, Plant/genetics , RNA, Plant/metabolism , Receptors, LDL/genetics , Receptors, LDL/metabolism , Receptors, Oxidized LDL , Recombinant Proteins , Solanum tuberosum/genetics , Suppression, Genetic , Transcription, GeneticABSTRACT
Transposon Tn5 was used to produce insertions within the region of a cyanobacterial shuttle vector previously identified as necessary for transformation of Anacystis nidulans. These transposon-containing plasmids were used to transform a plasmid-cured derivative of Anacystis strain R2 and tested for structural stability of the transforming plasmid. The transposon DNA was deleted from all the plasmids containing Tn5 within the cyanobacterial replication region. Inserts in the vector DNA were physically stable and expressed the kanr gene. The internal Tn5 HindIII fragment was also cloned into each of the three HindIII sites in the shuttle plasmid. Inserts in two of these sites were stable, whereas inserts into the third site were not.
