Cisgenic inhibition of the potato cold induced phosphorylase L gene expression and decrease in sugar contents
To decrease the accumulation of reducing and non-reducing sugar in potato tubers stored at low temperature, a single gene silencing vector pARTPhL-IR, harboring a part of starch phosphorylase L gene as inverted repeats with pdk intron within was constructed and transformed into potato (Solanum tuberosum L.) cultivars Agria and Marfona. Polymerase chain reaction (PCR) of nptII gene and pdk intron indicated that the RNA interference construct was transformed successfully into the genome. Real time RT-PCR analysis of starch phosphorylase L gene in stored microtubers for 90 days at 4°C showed that the expression level of this gene in transgenics ranged from 1.63 to 7.54% of that in the non-transgenic plants. Analysis of sugar content in these plants showed that the total sugar content in transgenic microtubers was significantly reduced compared to the control, up to 35% in line M4. The accumulation of reducing sugars in transgenic lines at 4°C was reduced from 9.13 (in Agria) to 5.57 mg/g fresh weight (transgenic line A5) and from 9.56 (in Marfona) to 6.52 mg/g fresh weight (transgenic line M4), implying that silencing of starch phosphorylase L gene reduced starch breakdown during cold storage conditions.
Key words: Cold sweetening, potato (Solanum tuberosum L.), RNA interference, starch phosphorylase L. gene,