Key Gene Influences Photosynthesis in Aging Tomato Leaves

Jenn Hoskins
11th July, 2024

Key Gene Influences Photosynthesis in Aging Tomato Leaves

Image Source: Natural Science News, 2024

Key Findings

  • The study from Shandong Agricultural University found that melatonin helps delay leaf aging in tomato plants under darkness and aging conditions
  • Overexpressing the SlTDC gene in tomato plants increased melatonin levels, which maintained higher chlorophyll content and photosynthetic efficiency
  • Conversely, knocking out the SlTDC gene accelerated leaf aging, highlighting melatonin's protective role in plant health
Melatonin (MT) has been identified as a key regulator in plants' response to leaf senescence—a process of aging and degradation of leaf tissue. A recent study by researchers at Shandong Agricultural University has provided new insights into how melatonin can mitigate leaf senescence in tomato plants under conditions of darkness and aging[1]. Leaf senescence is a complex and highly regulated process that can be triggered by both internal factors, such as aging, and external abiotic stresses like darkness, drought, and extreme temperatures[2]. Previous studies have shown that melatonin is present in plants and plays a role in alleviating various stress conditions, including foliar senescence[3][4]. The current research builds on these findings by exploring the specific mechanisms through which melatonin influences leaf aging and stress responses in tomato plants. The study demonstrated that both darkness and leaf aging enhance the levels of endogenous melatonin in tomato plants by upregulating key genes involved in melatonin synthesis. This increase in endogenous melatonin helps mitigate the senescence process, leading to higher chlorophyll content and improved maximum photochemical efficiency (Fv/Fm) in treated plants compared to controls. Chlorophyll is essential for photosynthesis, and its degradation is a hallmark of leaf senescence. To further investigate the role of melatonin, the researchers used transgenic tomato seedlings with either overexpressed or knocked-out Solanum lycopersicum L. tryptophan decarboxylase (SlTDC), a key enzyme in melatonin synthesis. Overexpression of SlTDC resulted in increased endogenous melatonin levels and suppressed the expression of genes related to chlorophyll degradation, such as pheophorbide a oxygenase (PAO), pheophytinase (PPH), and non-yellow coloring1 like (NOL). This suppression helps maintain chlorophyll levels and delays the senescence process. Additionally, the overexpression of SlTDC alleviated photoinhibition of the photosystem II complex (PSII), increased the activities and mRNA levels of ribulose-1,5-bisphosphate carboxylase (Rubisco) and Rubisco activase (RCA), and maintained higher photosynthetic efficiency under darkness and aging conditions. Rubisco is a crucial enzyme in the Calvin-Benson cycle, which is essential for carbon fixation during photosynthesis[5]. Conversely, knocking out SlTDC accelerated leaf senescence under the same conditions, highlighting the protective role of melatonin. These findings align with earlier studies that have shown melatonin's ability to delay senescence and protect photosynthetic systems in plants[3][4]. For instance, melatonin has been found to slow down the senescence process in barley leaves by preserving chlorophyll content[3]. Moreover, melatonin's role as a multi-regulatory molecule in plants has been well-documented, with its involvement in stress responses, growth regulation, and immune responses[4]. The current study from Shandong Agricultural University expands our understanding of melatonin's role in regulating photosynthesis and leaf senescence in tomato plants. By demonstrating that exogenous melatonin application or SlTDC overexpression can effectively alleviate leaf senescence, the research provides a potential strategy for improving plant resilience against aging and stress conditions. In summary, this study underscores the importance of melatonin in plant physiology, particularly in mitigating leaf senescence induced by darkness and aging. The findings suggest that enhancing melatonin levels in plants, either through genetic modification or exogenous application, could be a viable approach to maintaining plant health and productivity under various stress conditions.

GeneticsBiochemPlant Science

References

Main Study

1) SlTDC modulates photosynthesis of senescent leaves in tomato

Published 10th July, 2024

https://doi.org/10.1007/s44281-024-00039-2

Related Studies

2) The molecular analysis of leaf senescence--a genomics approach.

Journal: Plant biotechnology journal, Issue: Vol 1, Issue 1, Jan 2003

3) Protective effect of melatonin against chlorophyll degradation during the senescence of barley leaves.

https://doi.org/10.1111/j.1600-079X.2008.00625.x

4) Melatonin and its relationship to plant hormones.

https://doi.org/10.1093/aob/mcx114

5) Decreasing fructose-1,6-bisphosphate aldolase activity reduces plant growth and tolerance to chilling stress in tomato seedlings.

https://doi.org/10.1111/ppl.12682


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