Abstract
Plants perceive and transduce information about light quantity, quality, direction and photoperiod via several photoreceptors and use it to adjust their growth and development. A role for photoreceptors has been hypothesized in the injuries that tomato plants develop when exposed to continuous light as the light spectral distribution influences the injury severity. Up to now, however, only indirect clues suggested that phytochromes (PHY), red/far-red photoreceptors, are involved in the continuous-light-induced injuries in tomato. In this study, therefore, we exposed mutant and transgenic tomato plants lacking or over-expressing phytochromes to continuous light, with and without far-red light enrichment. The results show that PHYA over-expression confers complete tolerance to continuous light regardless the light spectrum. Under continuous light with low far-red content, PHYB1 and PHYB2 diminished and enhanced the injury, respectively, yet the effects were small. These results confirm that phytochrome signaling networks are involved in the induction of injury under continuous light.HIGHLIGHTS- PHYA over-expression confers tolerance to continuous light regardless the light spectrum.- In the absence of far-red light, PHYB1 slightly diminishes the continuous light-induced injury.- Continuous light down-regulates photosynthesis genes in sensitive tomato lines.
Highlights
Sunlight is essential for life on earth
Two-week-old plants of tomato wild-type, phy mutants and PHYOE lines were exposed to continuous light (CL) provided by high-pressure sodium (HPS) light, with and without addition of far-red light
After 2 weeks of treatment, all tomato lines grown under 16h photoperiod showed maximum quantum efficiency of photosystem II (Fv/Fm) values that were not significantly different from the wild-type Moneymaker plants (P > 0.05), and were similar to those reported in the literature for non-stressed healthy leaves (Baker, 2008)
Summary
Sunlight is essential for life on earth. Plants have developed a photosynthetic machinery to harvest the energy from the sun and a set of photoreceptors that can sense light quality, quantity, direction and photoperiod, allowing them to adjust their growth and development according to the light environment (Christie, 2007; Jiao et al, 2007; Bae and Choi, 2008; Moglich et al, 2010). A remarkable example, first reported by Arthur et al (1930), are the injuries that domesticated tomatoes develop when exposed to continuous light (CL), which include mottled chlorosis and poor photosynthetic performance. It is still unclear if the altered photosynthetic performance is a cause or consequence, and which of the light signaling mechanisms plays a role, if any. Based on evidence accumulated over the years and a modern understanding of plant physiology, we previously proposed that both, photosynthesis and light signaling might play a role in the development of the injury in CL-grown tomato plants (VelezRamirez et al, 2011)
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