Photoregulation of the Greening Process of Wheat Seedlings Grown in Red Light* |
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Authors: | Suchi?Sood Varsha?Gupta Email author" target="_blank">Baishnab?C?TripathyEmail author |
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Institution: | (1) School of Life Sciences, Jawaharlal Nehru University, 110067, New Delhi, India |
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Abstract: | Wheat seedling grown with their shoot bottom exposed to red light (400 μmol m−2 s−1) either with constant illumination or light-dark cycles did not accumulate chlorophyll. This near-etiolation response was
manifested by a critical threshold intensity of red light and did not need continuous illumination. The inhibition of the
greening process resulted from reduced synthesis of glutamate-1-semialdehyde and consequent reduction in tetrapyrrole precursor
5-aminolevulinic acid. Red light perceived by the shoot bottom down regulated the protein and/or gene expression of enzymes
involved in the biosynthesis of tetrapyrroles. The contents of endogenous cytokinins, i.e., isopentenyl-adenosine and dihydrozeatinriboside,
were reduced in seedlings grown in red light having their shoot bottom exposed. Application of exogenous cytokinin and its
analogue to roots of seedlings grown in red light reversed the down regulation of the greening process. The reversal of red-light-induced
near-etiolation morphogenesis by far-red (200 μmol m−2 s−1) or blue (25 μmol m−2 s−1) light suggests that it could be a very high red-irradiance response of phytochrome, in the meristematic layers of the shoot
bottom, that works in concert with blue light receptor(s).
This work was supported by a competitive grant from the Department of Science and Technology, Govt. of India (DST/SP/SO/A-49/95)
to BCT.
Suchi Sood Varsha Gupta: Equal contributors |
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Keywords: | blue light chlorophyll biosynthesis cytokinin photoreceptor phytochrome red light |
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