Blue Light Inhibition of Tuberization in a Day-Neutral Potato

In tests on the effects of light quality on potato tuberization, continuous blue light was found to consistently inhibit tuberization of tissue-cultured plantlets of Solanum tuberosum ssp. tuberosum cv. 'Norland'. Other tested cultivars, including sports of 'Norland', formed tubers under continuous blue light. Microarrays identified BL, GA7ox, and Nudix genes as exhibiting altered expression in response to blue light treatment. Quantitative RT-PCR (qRT-PCR) showed that GA7ox RNA increased in 'Norland' but not in 'Sangre' plantlets in blue light compared to darkness. RNA levels of genes identified in the literature as having roles in potato tuberization were also measured using qRT-PCR. Levels of GA20o1x, but not GA2ox, RNA increased in response to blue light in 'Norland' plantlets. BEL5 RNA content was greater under blue light compared to darkness for both 'Norland' and 'Sangre' plants. Levels of FT were not significantly different in blue light compared to dark-treated 'Norland' plants, but were low in blue light-treated compared to dark-treated 'Sangre' plants. Addition of ancymidol to 'Norland' plants exposed to blue light overcame blue light inhibition of tuberization. Ancymidol prevents the oxidation of ent-kaurene to ent-kaurenoic acid, thus inhibiting gibberellin biosynthesis. These data suggest that blue light may increase GA accumulation in 'Norland' plants, as has been shown to occur in Arabidopsis plants. The novel effect of blue light in inhibiting tuberization of 'Norland' plants suggests that this system could be a useful tool in further elucidating the mechanisms of day-neutral potato tuberization.