Abstract
Leaf senescence, the last stage of leaf development, is a type of postmitotic senescence and is characterized by the functional transition from nutrient assimilation to nutrient remobilization which is essential for plants’ fitness. The initiation and progression of leaf senescence are regulated by a variety of internal and external factors such as age, phytohormones, and environmental stresses. Significant breakthroughs in dissecting the molecular mechanisms underpinning leaf senescence have benefited from the identification of senescence-altered mutants through forward genetic screening and functional assessment of hundreds of senescence-associated genes (SAGs) via reverse genetic research in model plant Arabidopsis thaliana as well as in crop plants. Leaf senescence involves highly complex genetic programs that are tightly tuned by multiple layers of regulation, including chromatin and transcription regulation, post-transcriptional, translational and post-translational regulation. Due to the significant impact of leaf senescence on photosynthesis, nutrient remobilization, stress responses, and productivity, much effort has been made in devising strategies based on known senescence regulatory mechanisms to manipulate the initiation and progression of leaf senescence, aiming for higher yield, better quality, or improved horticultural performance in crop plants. This review aims to provide an overview of leaf senescence and discuss recent advances in multi-dimensional regulation of leaf senescence from genetic and molecular network perspectives. We also put forward the key issues that need to be addressed, including the nature of leaf age, functional stay-green trait, coordination between different regulatory pathways, source-sink relationship and nutrient remobilization, as well as translational researches on leaf senescence.
Highlights
Senescence is the final stage of plant development and is characterized by a series of programmed disassembly and degenerative events (Guo and Gan 2005; Lim et al 2007)
When does leaf senescence start? What is the molecular nature of age? How are external signals integrated into the plant internal age information? Is the regulatory mechanism of leaf senescence conserved among different plant species? What is the general mechanism of leaf senescence? In this article, we review recent advances in understanding leaf senescence and longevity through molecular, genetic and network analyses
Impressive progress has been achieved in understanding leaf senescence through forward/reverse genetic strategies and omics-based technologies, etc
Summary
Senescence is the final stage of plant development and is characterized by a series of programmed disassembly and degenerative events (Guo and Gan 2005; Lim et al 2007). The released nutrients are exported to other developing organs, such as new buds, young leaves, flowers (2021) 1:5 or seeds, which leads to increased reproductive success (Lim et al 2007) In perennial plants, such as deciduous trees, nutrients disassembled from senescent leaves are relocated to form bark storage proteins (BSP) in phloem tissues, stored over the winter, and remobilized and reutilized for shoot or flower growth during the growing season (Cooke and Weih 2005; Keskitalo et al 2005). Efficient senescence is critical for maximizing viability in the generation or season, while premature senescence induced by numerous environmental factors decreases the yield and fresh product quality of crop plants (Hortensteiner and Feller 2002). Understanding the regulatory mechanisms of leaf senescence will provide valuable clues and a theoretical basis for manipulation of this trait in agronomically important plants (Guo and Gan 2014)
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