Abstract
BackgroundPhytochromes are plant photoreceptors that have long been associated with photomorphogenesis in plants; however, more recently, their crucial role in the regulation of variety of abiotic stresses has been explored. Chilling stress is one of the abiotic factors that severely affect growth, development, and productivity of crops. In the present work, we have analyzed and compared physiological, biochemical, and molecular responses in two contrasting phytochrome mutants of tomato, namely aurea (aur) and high pigment1 (hp1), along with wild-type cultivar Micro-Tom (MT) under chilling stress. In tomato, aur is phytochrome-deficient mutant while hp1 is a phytochrome-sensitive mutant. The genotype-specific physiological, biochemical, and molecular responses under chilling stress in tomato mutants strongly validated phytochrome-mediated regulation of abiotic stress. ResultsHere, we demonstrate that phytochrome-sensitive mutant hp1 show improved performance compared to phytochrome-deficient mutant aur and wild-type MT plants under chilling stress. Interestingly, we noticed significant increase in several photosynthetic-related parameters in hp1 under chilling stress that include photosynthetic rate, stomatal conductance, stomatal aperture, transpiration rate, chlorophyll a and carotenoids. Whereas most parameters were negatively affected in aur and MT except a slight increase in carotenoids in MT plants under chilling stress. Further, we found that PSII quantum efficiency (Fv/Fm), PSII operating efficiency (Fq′/Fm′), and non-photochemical quenching (NPQ) were all positively regulated in hp1, which demonstrate enhanced photosynthetic performance of hp1 under stress. On the other hand, Fv/Fm and Fq′/Fm′ were decreased significantly in aur and wild-type plants. In addition, NPQ was not affected in MT but declined in aur mutant after chilling stress. Noticeably, the transcript analysis show that PHY genes which were previously reported to act as molecular switches in response to several abiotic stresses were mainly induced in hp1 and repressed in aur and MT in response to stress. As expected, we also found reduced levels of malondialdehyde (MDA), enhanced activities of antioxidant enzymes, and higher accumulation of protecting osmolytes (soluble sugars, proline, glycine betaine) which further elaborate the underlying tolerance mechanism of hp1 genotype under chilling stress. ConclusionOur findings clearly demonstrate that phytochrome-sensitive and phytochrome-deficient tomato mutants respond differently under chilling stress thereby regulating physiological, biochemical, and molecular responses and thus establish a strong link between phytochromes and their role in stress tolerance.
Highlights
Phytochromes are plant photoreceptors that have long been associated with photomorphogenesis in plants; more recently, their crucial role in the regulation of variety of abiotic stresses has been explored
We found that photosynthetic rate, stomatal conductance, and transpiration rate were significantly increased in tomato phytochrome-sensitive hp1 mutant upon subjecting to chilling stress (Fig. 1)
The confocal microscope examination indicated no significant differences in pore width between the wild-type MT and both aur and hp1 mutants under control condition (Fig. 2)
Summary
Phytochromes are plant photoreceptors that have long been associated with photomorphogenesis in plants; more recently, their crucial role in the regulation of variety of abiotic stresses has been explored. The genotype-specific physiological, biochemical, and molecular responses under chilling stress in tomato mutants strongly validated phytochrome-mediated regulation of abiotic stress. To explore the functional role of phytochromes in plants, its mutants with disruption in biosynthesis or signal transduction could be utilized These mutants can be helpful in determining phytochrome activity and its correlation with morpho-physiological responses and sometimes referred to as “photomorphogenic mutants” in plants. In tomato (Solanum lycopersicum L.) plants, the aurea (aur) mutant is phytochrome deficient, while the high pigment (hp1) mutant is highly sensitive to light-dependent responses [3]. Given the fact that phytochromes are associated with number of environmental factors, we still lack exact knowledge and underlying regulatory mechanisms of phytochromes in response to different stress factors
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
