Previous research suggests that the senescence and death of the replaceable bud in chestnut cultivar (cv.) ‘Tima Zhenzhu’ involves programmed cell death (PCD). However, the molecular network responsible for regulating replaceable bud PCD is poorly characterized. Here, we performed transcriptomic profiling of the chestnut cv. ‘Tima Zhenzhu’ replaceable bud before (S20), during (S25), and after PCD (S30) to ascertain the molecular mechanism underlying the PCD process. A total of 5,779, 9,867, and 2,674 differentially expressed genes (DEGs) were discovered upon comparison of S20 vs. S25, S20 vs. S30, and S25 vs. S30, respectively. Approximately 6,137 DEGs common to at least two comparisons were selected for GO and KEGG enrichment analyses to interrogate the main corresponding biological functions and pathways. GO analysis showed that these common DEGs could be divided into three functional categories, including 15 cellular components, 14 molecular functions, and 19 biological processes. KEGG analysis found that “plant hormone signal transduction” included 93 DEGs. Overall, 441 DEGs were identified as related to the process of PCD. Most of these were found to be genes associated with ethylene signaling, as well as initiation and execution of various PCD processes. A hypothetical model, consisting of three overlapping processes, is proposed for the replaceable bud PCD: First, ethylene signaling is activated during preparation for PCD, in order to regulate the activity of downstream targets. Next, during PCD initiation, the up-regulation of several TFs (including MYB, MADS-box, bHLH, and NAC TFs) induces an increase in cytochrome c expression and in the cytosolic Ca2+ content, activating the Ca2+-dependent signaling cascade. Finally, during PCD execution, the process of autophagy and the activity of proteases (i.e., cysteine proteinases RD21A-like, metacaspase-9-like, vacuolar-processing enzyme-like, and senescence-associated proteins for hydrolysis) work synergistically to clear the cell of cellular components. When this process is complete, the replaceable bud senesces and dies.

Previous studies suggest that the senescence and death of the replaceable bud of the Chinese chestnut cultivar (cv.) “Tima Zhenzhu” involves programmed cell death (PCD). However, the molecular network regulating replaceable bud PCD is poorly characterized. Here, we performed transcriptomic profiling on the chestnut cv. “Tima Zhenzhu” replaceable bud before (S20), during (S25), and after (S30) PCD to unravel the molecular mechanism underlying the PCD process. A total of 5,779, 9,867, and 2,674 differentially expressed genes (DEGs) were discovered upon comparison of S20 vs S25, S20 vs S30, and S25 vs S30, respectively. Approximately 6,137 DEGs common to at least two comparisons were selected for gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses to interrogate the main corresponding biological functions and pathways. GO analysis showed that these common DEGs could be divided into three functional categories, including 15 cellular components, 14 molecular functions, and 19 biological processes. KEGG analysis found that “plant hormone signal transduction” included 93 DEGs. Overall, 441 DEGs were identified as related to the process of PCD. Most of these were found to be genes associated with ethylene signaling, as well as the initiation and execution of various PCD processes.