Abstract
Leaf senescence is a complex organized developmental stage limiting the yield of crop plants, and alfalfa is an important forage crop worldwide. However, our understanding of the molecular mechanism of leaf senescence and its influence on biomass in alfalfa is still limited. In this study, RNA sequencing was utilized to identify differentially expressed genes (DEGs) in young, mature, and senescent leaves, and the functions of key genes related to leaf senescence. A total of 163,511 transcripts and 77,901 unigenes were identified from the transcriptome, and 5,133 unigenes were differentially expressed. KEGG enrichment analyses revealed that ribosome and phenylpropanoid biosynthesis pathways, and starch and sucrose metabolism pathways are involved in leaf development and senescence in alfalfa. GO enrichment analyses exhibited that six clusters of DEGs are involved in leaf morphogenesis, leaf development, leaf formation, regulation of leaf development, leaf senescence and negative regulation of the leaf senescence biological process. The WRKY and NAC families of genes mainly consist of transcription factors that are involved in the leaf senescence process. Our results offer a novel interpretation of the molecular mechanisms of leaf senescence in alfalfa.
Highlights
Leaves are key photosynthetic organs that produce carbohydrates that provide energy for plant development
We found 25 differentially expressed genes (DEGs) involved in leaf development process (Fig. 4B). c111950.graph_c1, MUB3.9 and Tubulin gamma-1 chain (TUBG1) were identified as novel genes in alfalfa
A total of 163,511 transcripts and 77,901 unigenes were identified from the transcriptomes
Summary
Leaves are key photosynthetic organs that produce carbohydrates that provide energy for plant development. The leaf undergoes three main developmental phases: initial leaves, maturation, and senescence (Buchanan-Wollaston, 1997). Much more nutrient input is initially needed to support leaf growth and development. The mature leaves are mainly responsible for providing a source of carbon, and this function continues until the onset of senescence. The nutrients in leaves, including nitrogen, metals, and phosphorus, are reallocated to other tissues and organs to support plant development. The leaf cells undergo significant changes in their cellular metabolism and cellular structures are degenerated (Rattan & Hayflick, 2016; Buchanan-Wollaston, 1997; Zentgraf et al, 2004; Nam, 1997). Leaf senescence is a complex organized developmental
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