Abstract
Light is the primary regulator of various biological processes during the plant life cycle. Although plants utilize photosynthetically active radiation to generate chemical energy, they possess several photoreceptors that perceive light of specific wavelengths and then induce wavelength-specific responses. Light is also one of the key determinants of the initiation of leaf senescence, the last stage of leaf development. As the leaf photosynthetic activity decreases during the senescence phase, chloroplasts generate a variety of light-mediated retrograde signals to alter the expression of nuclear genes. On the other hand, phytochrome B (phyB)-mediated red-light signaling inhibits the initiation of leaf senescence by repressing the phytochrome interacting factor (PIF)-mediated transcriptional regulatory network involved in leaf senescence. In recent years, significant progress has been made in the field of leaf senescence to elucidate the role of light in the regulation of nuclear gene expression at the molecular level during the senescence phase. This review presents a summary of the current knowledge of the molecular mechanisms underlying light-mediated regulation of leaf senescence.
Highlights
Leaf senescence, the final stage of leaf development, is a highly controlled developmental process accompanied by massive transcriptional and metabolic changes that destabilize intracellular organelles and macromolecules and translocate nutrients into developing tissues and storage organs
In dark-grown flu mutant seedlings, incubation under light for 2 h significantly upregulated the expression of several stress-responsive genes including ABSCISIC ACID (ABA) INSENSITIVE 1 (ABI1), which encodes a protein phosphatase that acts as a negative regulator of ABA signaling [47], and 1-AMINOCYCLOPROPANE-1-CARBOXYLATE OXIDASE 4 (ACO4), which encodes an ethylene biosynthesis enzyme [48]
Silencing of SlPIF4 via RNA interference (RNAi) delayed leaf yellowing during the senescence phase and downregulated several senescence-associated genes (SAGs), such as SlSGR1, SlSAG12, and SlORE1 [98]. These findings suggest that SlPIF4 promotes leaf senescence by modulating downstream transcriptional cascades, similar to Arabidopsis PIF4 and PIF5
Summary
The final stage of leaf development, is a highly controlled developmental process accompanied by massive transcriptional and metabolic changes that destabilize intracellular organelles and macromolecules and translocate nutrients into developing tissues and storage organs. Numerous studies conducted in the past two decades have greatly expanded our knowledge of the molecular mechanisms underlying the regulation of leaf senescence (reviewed in [1,2,3,4,5]). Light is the foremost regulator of various biological processes in the plant life cycle. Light characteristics, such as wavelength, fluence rate, and photoperiod, greatly affect plant traits, including growth habit, floral induction, and plant productivity [13]. Molecular mechanisms underlying photosynthesis- and light-signaling-mediated regulation of leaf senescence have been uncovered. This review highlights the significance of both photosynthesis and light signaling in the regulation of leaf senescence
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