Blue light inhibition of tuberization

A tuberization inhibitor has long been postulated, but not yet found. We found that blue light inhibits tuberization in Norland, a day-neutral variety of Solanum tuberosum L. Tissue-cultured plants formed tubers within 8 weeks under continuous darkness, and white, red, or far-red light. Preliminary experiments indicated that a one- or two-day exposure to blue light after 3-4 weeks of dark treatment will inhibit tuber formation in ‘Norland’ plants. Using this system and expression profiling, we may be able to identify candidate tuberization inhibitors. 'Norland' plants (subcultured from existing cultures and grown for two weeks under continuous 100 umol/m2-s white fluorescent light) were placed in tuber-inducing media containing 6% sucrose, vitamins, MS salts, and kinetin (2.5 mg/L). Tubes containing plants were wrapped in two layers of aluminum foil. After 3 weeks and 2 days, half of the tubes were exposed to 6-7 umol/m2-s blue light. The other half of the tubes were left in darkness (controls). After 2 days, all plants were harvested and frozen in liquid nitrogen. Plants exposed to blue light were harvested under blue light. Control plants were harvested under < 2 umol/m2-s light conditions. All plant transfers were done at 1700 (5 PM) to avoid possible complications due to circadian effects. Experiments were performed four times, from subculture to harvest. RNA was extracted from stem and leaf tissue of plants using the Qiagen RNeasy Plant Mini kit. Extracted RNA was then converted to dsDNA using the Invitrogen protocol and reagents for double stranded cDNA synthesis. The resulting dsDNA was in vitro transcribed into amplified RNA using the Ambion procedure and reagents for in vitro transcription. cDNA was purified using Qiagen MinElute columns and protocol. Amplified RNA was purified using Ambion columns or Qiagen RNeasy columns and the Ambion protocol, and quantified using RiboGreen dye fluorometry. Keywords: Direct comparison 6 hybs total