BACKGROUND: Tuberization in potato (Solanum tuberosum L.) represents a morphogenetic transition of stolon growth to tuber formation, which is under complex environmental and endogenous regulation. In the present work, we studied the regulatory mechanisms and the role of different morphogenetic factors in a newly isolated potato mutant, which exhibited spontaneous tuberization (ST). The ST mutant was characterized in detail at morphological, physiological and biochemical levels. RESULTS: Tuberization of the ST mutant grown in the soil was photoperiod-insensitive; predominantly sessile tubers formed directly from axillary buds even under continuous light. Single-node cuttings of the ST mutant cultured in vitro frequently formed tubers or basal tuber-like swellings instead of normal shoots under conditions routinely used for shoot propagation. The tuberization response of ST cuttings under light was dependent on sucrose, the concentration of which had to exceed certain threshold that inversely correlated with irradiance. Gibberellic acid prevented tuberization of ST cuttings, but failed to restore normal shoot phenotype and caused severe malformations. Carbohydrate analysis showed increased levels of both soluble sugars and starch in ST plants, with altered carbohydrate partitioning and metabolism. Comparative proteomic analysis revealed only a few differences between ST- and wild-type plants, primary amongst which seemed to be the absence of an isoform of manganese-stabilizing protein, a key subunit of photosystem II. CONCLUSION: ST mutant exhibits complex developmental and phenotypic modifications, with features that are typical for plants strongly induced to tuberize. These changes are likely to be related to altered regulation of photosynthesis and carbohydrate metabolism rather than impaired transduction of inhibitory gibberellin or photoperiod-based signals. The effect of gibberellins on tuberization of ST mutant suggests that gibberellins inhibit tuberization downstream of the inductive effects of sucrose and other positive factors.

• MeSH
• Biomass MeSH
• DNA, Bacterial metabolism   MeSH
• Photoperiod MeSH
• Gibberellins pharmacology   MeSH
• Plant Tubers drug effects   genetics   metabolism   radiation effects   MeSH
• Mutagenesis, Insertional MeSH
• Plant Leaves drug effects   metabolism   radiation effects   MeSH
• Carbohydrate Metabolism drug effects   radiation effects   MeSH
• Mutation genetics   MeSH
• RNA, Untranslated genetics   MeSH
• Proteome metabolism   MeSH
• Soil MeSH
• Gene Expression Regulation, Plant drug effects   radiation effects   MeSH
• DNA, Ribosomal genetics   MeSH
• Genes, Plant MeSH
• Sucrose pharmacology   MeSH
• Starch metabolism   MeSH
• Solanum tuberosum drug effects   genetics   metabolism   radiation effects   MeSH
• Plant Stems drug effects   metabolism   radiation effects   MeSH
• Light MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• DNA, Bacterial MeSH
• gibberellic acid MeSH Browser
• Gibberellins MeSH
• RNA, Untranslated MeSH
• Proteome MeSH
• Soil MeSH
• DNA, Ribosomal MeSH
• Sucrose MeSH
• Starch MeSH
• T-DNA MeSH Browser

We have isolated the cDNA of the gene PaLAX1 from a wild cherry tree (Prunus avium). The gene and its product are highly similar in sequences to both the cDNAs and the corresponding protein products of AUX/LAX-type genes, coding for putative auxin influx carriers. We have prepared and characterized transformed Nicotiana tabacum and Arabidopsis thaliana plants carrying the gene PaLAX1. We have proved that constitutive overexpression of PaLAX1 is accompanied by changes in the content and distribution of free indole-3-acetic acid, the major endogenous auxin. The increase in free indole-3-acetic acid content in transgenic plants resulted in various phenotype changes, typical for the auxin-overproducing plants. The uptake of synthetic auxin, 2,4-dichlorophenoxyacetic acid, was 3 times higher in transgenic lines compared to the wild-type lines and the treatment with the auxin uptake inhibitor 1-naphthoxyacetic acid reverted the changes caused by the expression of PaLAX1. Moreover, the agravitropic response could be restored by expression of PaLAX1 in the mutant aux1 plants, which are deficient in auxin influx carrier activity. Based on our data, we have concluded that the product of the gene PaLAX1 promotes the uptake of auxin into cells, and, as a putative auxin influx carrier, it affects the content and distribution of free endogenous auxin in transgenic plants.

• MeSH
• Arabidopsis enzymology   genetics   MeSH
• Gene Expression MeSH
• Phenotype MeSH
• Phylogeny MeSH
• Plants, Genetically Modified enzymology   MeSH
• Gravitropism physiology   MeSH
• DNA, Complementary MeSH
• Flowering Tops metabolism   MeSH
• 2,4-Dichlorophenoxyacetic Acid MeSH
• Indoleacetic Acids metabolism   MeSH
• Plant Leaves metabolism   MeSH
• Membrane Transport Proteins genetics   metabolism   MeSH
• Molecular Sequence Data MeSH
• Amino Acid Sequence MeSH
• Prunus enzymology   genetics   MeSH
• Nicotiana enzymology   genetics   MeSH
• Genetic Complementation Test MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• DNA, Complementary MeSH
• 2,4-Dichlorophenoxyacetic Acid MeSH
• Indoleacetic Acids MeSH
• Membrane Transport Proteins MeSH