Photoreceptors in plant
In a wide range, plants need light for growth and development. During photosynthesis, plants convert light into energy. Captruing sunlight is mediated by plant photorecpetors, which are plant proteins that perceive, receive, and transmit signals for biological functions in plants. Sveral plant photoreceptors have been reported, among which, phytocrhome and cryptochrome, and phototropin known to perceive red.far-red and blue-light, respectively. Light Controls Protein Localization through Phytochrome-Mediated Alternative Promoter Selection (Ushijima, et al. 2017).
Biological fuctions of light in plants
Photosynthesis
Photosynthesis is the process in which light energy is converted into chemical energy. Using the energy of light, carbohydrates such as sugars are synthesised from carbon dioxide and water. The process of photosynthesis occurs when green plants use the energy of light to convert carbon dioxide (CO2) and water (H2O) into carbohydrates. Light energy is absorbed by chlorophyll, a photosynthetic pigment of the plant, while air containing carbon dioxide and oxygen enters the plant through the leaf stomata. An extremely important by-product of photosynthesis is oxygen, on which most organisms depend
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Germination
Phytochrome are one of the most photorecptors that play a key role in seed germination under fluctuating lights conditions. For example, studies showed that phyA can act by sensonring low light, whereas phyB was reported to mediate red/far-red reversible induction of seed germination.
Plant vegetative growth
Plant photoreceptors promote vegetative plant growth depending on the available light conditons. The shade avoidance response (SAR) is a good illustration of this concept. Shade from the vegetation has a distinct spectral signature, which has a strong influence on the phytochrome photoequilibrium due to alterations of the R:FR ratio.
Transition to flowering
Both light and temperature influence the transition from vegetative to reproductive growth. The phytochromes, cryptochromes, and members of the Zeitlupe family all contribute to this complex regulatory network, either by acting directly on key regulators of floral transition such as
CONSTANS (CO) or by modulating the circadian clock, which has a profound influence on photoperiodic flowering
Light sensing and pathogen defense
Light is required to mount an efficient response to pathogens in Arabidopsis. Especially, light is important during the first hours following inoculation as dark-infected plants support more bacterial growth and mount less-efficient defense mechanisms than light-infected plants. PhyA, phyB, and cry1 are involved in the resistance response to Pseudomonas syringae pv. tomato carrying the AvrRpt2 gene.
References
- Kami, C., Lorrain, S., Hornitschek, P., & Fankhauser, C. (2010). Light-regulated plant growth and development. In Current topics in developmental biology (Vol. 91, pp. 29-66). Academic Press.
- Kong, S. G., & Okajima, K. (2016). Diverse photoreceptors and light responses in plants. Journal of plant research, 129(2), 111-114.
- Kong, SG. & Okajima, K. J Plant Res (2016) 129: 111. https://doi.org/10.1007/s10265-016-0792-5
- Ushijima, T., Hanada, K., Gotoh, E., Yamori, W., Kodama, Y., Tanaka, H., ... & Tada, Y. (2017). Light controls protein localization through phytochrome-mediated alternative promoter selection. Cell, 171(6), 1316-1325.
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