Abstract
Leaf senescence represents the final stage of leaf development and is regulated by diverse internal and environmental factors. Jasmonates (JAs) have been demonstrated to induce leaf senescence in several species; however, the mechanisms of JA-induced leaf senescence remain largely unknown in tomato plants (Solanum lycopersicum). In the present study, we tested the hypothesis that sedoheptulose-1,7-bisphosphatase (SBPase), an enzyme functioning in the photosynthetic carbon fixation in the Calvin–Benson cycle, was involved in methyl jasmonate (MeJA)- and dark-induced leaf senescence in tomato plants. We found that MeJA and dark induced senescence in detached tomato leaves and concomitantly downregulated the expression of SlSBPASE and reduced SBPase activity. Furthermore, CRISPR/Cas9 (clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9)-mediated mutagenesis of SlSBPASE led to senescence-associated characteristics in slsbpase mutant plants, including loss of chlorophyll, repressed photosynthesis, increased membrane ion leakage, and enhanced transcript abundance of senescence-associated genes. Collectively, our data suggest that repression of SBPase by MeJA and dark treatment plays a role in JA- and dark-induced leaf senescence.
Highlights
Leaf senescence represents the final stage of leaf development and is a crucial phase of plant life cycle
These results indicate that 100 μM methyl jasmonate (MeJA) is effective in the induction of senescence in tomato leaves
A large number of studies on the elucidation of JA-induced leaf senescence are confined to the model species Arabidopsis thaliana and our knowledge on the role of JA in the induction of leaf senescence in a horticultural crop species, such as Solanum lycopersicum, is rather scanty
Summary
Leaf senescence represents the final stage of leaf development and is a crucial phase of plant life cycle. Leaf senescence leads to the remobilization of nutrients and energy to younger developing tissues and storage organs, which ensures offspring production and better survival in plants under certain circumstances [1,2,3]. Leaf senescence occurs dependent on developmental age. Unfavorable environmental factors, such as drought, dark, extreme temperatures, salinity, nutrient deficiency, heavy metal toxicity, and pathogens, trigger premature leaf senescence [2,4]. In addition to environmental cues, internal factors, including phytohormones and metabolites, induce leaf senescence [2,5,6,7]. Leaf senescence is generally featured by rapid degradation of chlorophyll, suppression of photosynthetic capacity and increased expression of senescence-related genes, including SENESCENCE-ASSOCIATED GENE12 (SAG12) and SENESCENCE4 (SEN4) [8,9,10,11]
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