Disease relevance of CYT1

• Infection with either virulent Pseudomonas syringae or Peronospora parasitica resulted in largely reduced bacterial and hyphal growth in the vtc1 mutant in comparison to the wild type [1].

High impact information on CYT1

• Cytokinesis-defective mutant sectors were observed in all somatic tissues upon transformation of wild-type plants with a KEULE-green fluorescent protein gene fusion, suggesting that KEULE is required not only during embryogenesis, but at all stages of the plant's life cycle [2].
• Ala420 is a conserved amino acid in the AtMAP65 family and is mutated to Val in the cytokinesis-defective mutant pleiade-4 of the AtMAP65-3/PLEIADE gene [3].
• This finding provides evidence that many of the observed effects on transcript abundance in vtc1 result from ascorbate deficiency [4].
• Furthermore, transcript changes indicate that growth and development are constrained in vtc1 by the modulation of abscisic acid signaling [4].
• Abscisic acid contents are significantly higher in vtc1 than in the wild type [4].

Chemical compound and disease context of CYT1

• Here we show that the Arabidopsis (Arabidopsis thaliana) low vitamin C mutants, vtc1 and vtc2, which have between 10% and 25% of wild-type ascorbic acid, exhibit microlesions, express pathogenesis-related (PR) proteins, and have enhanced basal resistance against infections caused by Pseudomonas syringae [5].

Biological context of CYT1

• These features indicate that CYT1 plays an essential and unique role in plant growth and development and the establishment of normal cell-wall architecture [6].
• Characteristic aspects of the cyt1 phenotype, including radial swelling and accumulation of callose, can be mimicked with the inhibitor of N-glycosylation, tunicamycin [7].
• Arabidopsis cyt1 mutants are deficient in a mannose-1-phosphate guanylyltransferase and point to a requirement of N-linked glycosylation for cellulose biosynthesis [7].
• Presumably, therefore, low AsA is causing vtc1 to enter at least some stage(s) of senescence prematurely with an accompanying increase in salicylic acid levels that results in a faster induction of defense responses [1].
• Consistent with the proposed role for ascorbate in reactive oxygen species detoxification, lipid peroxides are elevated in soz1, but not in wild type following ozone fumigation [8].

Anatomical context of CYT1

• PCD symptoms such as nuclear chromatin condensation, the presence of multivesicular bodies, and extensive degradation and disorganization of the grana stacks were observed in 8-week-old vtc2 leaves and in 10-week-old vtc1 leaves [9].
• Consistent with a role for SCD1 in membrane trafficking, secretory vesicles were found to accumulate in cytokinesis-defective scd1 cells [10].

Associations of CYT1 with chemical compounds

• To determine the molecular basis of these defects, we have cloned the CYT1 gene by a map-based approach and found that it encodes mannose-1-phosphate guanylyltransferase [7].
• However, the vtc2 mutants produced greater numbers of longer LRs than wild-type or vtc1 plants at all levels of nitrate [9].
• A weak mutation in the same gene, called vtc1, has previously been identified on the basis of ozone sensitivity due to reduced levels of ascorbic acid [7].
• Some cyt1 defects can be partially phenocopied by treatment with the herbicide dichlobenil, which is thought to interfere with cellulose biosynthesis [6].
• The vtc1 defect does not appear to be the result of a deficiency in L-galactono-1,4-lactone dehydrogenase, an enzyme able to convert L-galactono-1,4-lactone to ascorbic acid [11].

Other interactions of CYT1

• In addition, the vtc1 mutant exhibits elevated levels of some senescence-associated gene (SAG) transcripts as well as heightened salicylic acid levels [1].
• By comparative in situ hybridisation to embryo sections, the 35S promoter yielded, relative to the endogenous KNOLLE promoter, low levels of KNOLLE mRNA accumulation in proliferating cells that were insufficient to rescue cytokinesis-defective knolle mutant embryos [12].

Analytical, diagnostic and therapeutic context of CYT1

• By using a combination of biochemical, molecular, and genetic techniques, we have demonstrated that the VTC1 locus encodes a GDP-mannose pyrophosphorylase (mannose-1-P guanyltransferase) [13].
• A novel Arabidopsis mutation, cytokinesis defective1 (cyd1), was identified by partial or missing cell walls in stomata [14].

References