UV-A light induces anthocyanin biosynthesis in a manner distinct from synergistic blue + UV-B light and UV-A/blue light responses in different parts of the hypocotyls in turnip seedlings.
The effects of irradiating blue, UV-A, UV-B and a combination of the lights on anthocyanin accumulation at different hypocotyl positions were investigated in seedlings of the purple top turnip 'Tsuda'. The location of anthocyanin accumulation varied depending on different light spectra. Stronger accumulation of anthocyanin was induced (i) at the upper hypocotyl positions by blue light; (ii) mainly at the upper position, but also at the middle position by UV-B light; and (iii) at the upper to lower position by UV-A light. There were synergistic effects between blue and UV-B, while such effects were not observed for the other light combinations. Among the six chalcone synthase (CHS) genes identified in the 'Tsuda' turnip, BrCHS1, 4 and 5 exhibited light-dependent expression patterns, while the other three showed no apparent light responses. The expression of BrCHS1, 4 and 5 was increased particularly by UV-A and blue + UV-B irradiation at the middle to lower hypocotyl positions, in accordance with anthocyanin accumulation patterns. The highest induction of gene expression was observed for BrCHS4 upon blue + UV-B co-irradiation. In contrast, CHS expression was induced only slightly at higher hypocotyl positions by blue light. The R2R3-type MYB transcription factor genes PAP1, MYB4, MYB12 and MYB111 exhibited differential expression patterns at different hypocotyl positions; these patterns were unique for different light spectra. These unique anthocyanin accumulation patterns and gene expression profiles depending on hypocotyl positions and light sources demonstrate that there is a distinct UV-A response, blue + UV-B synergistic response and blue/UV-A light response for anthocyanin biosynthesis in turnip. UV-A light-dependent anthocyanin biosynthesis appeared to be regulated in a manner that is distinct from that mediated by cryptochromes and UV-B photoreceptors.
College of Life Science, Northeast Forestry University, Harbin 150040, PR China.
Yu
Y
Wang
Bo
B
Zhou
Mei
M
Sun
Yuhua
Y
Li
Saneyuki
S
Kawabata
D000217:Acyltransferases / Q000235:genetics; D000429:Alcohol Oxidoreductases / Q000235:genetics; D000872:Anthocyanins / Q000096:biosynthesis*; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics; D029688:Brassica napus / Q000378:metabolism* / Q000528:radiation effects*; D056931:Cryptochromes; D004307:Dose-Response Relationship, Radiation; D018506:Gene Expression Regulation, Plant; D018546:Hypocotyl / Q000378:metabolism* / Q000528:radiation effects; D008027:Light; D000073718:Pancreatitis-Associated Proteins; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D017382:Reactive Oxygen Species; D036226:Seedlings / Q000378:metabolism* / Q000528:radiation effects; D013997:Time Factors; D014157:Transcription Factors / Q000235:genetics; D014466:Ultraviolet Rays
D000217:Acyltransferases; D000429:Alcohol Oxidoreductases; D000872:Anthocyanins; D051792:Basic Helix-Loop-Helix Proteins; D056931:Cryptochromes; D000073718:Pancreatitis-Associated Proteins; D010940:Plant Proteins; D017382:Reactive Oxygen Species; D014157:Transcription Factors; C000612141:REG3A protein, human; C056570:dihydroflavanol 4-reductase; C020141:flavanone synthetase