Transcriptome analysis unravels key pathways and hub genes related to immature fruit abscission in Camellia oleifera

Immature fruit abscission of <i>Camellia oleifera</i> (<i>C. oleifera</i>) is a common problem limiting yield increases. However, the regulatory mechanisms underlying immature fruit abscission in <i>C. oleifera</i> are unclear. In this study, we systematically investigated changes in the morphological, physiological, and gene expression of fruit abscission zones (FAZs) of soon-to-abscise fruits (M2). We found that fruit abscission before ripening mainly occurs during the August abscission stage of 'Huashuo'. At the beginning of this stage, the FAZs of M2 have a marked dent, and the separation layer structures are preliminarily formed. Phytohormone analysis showed that the contents of indole-3-acetic acid (IAA) and jasmonic acid (JA) in the FAZs of M2 were significantly decreased compared with the non-abscised fruits, while the content of <i>trans</i>-zeatin (TZR) was increased. Transcriptome analysis identified differentially expressed genes (DEGs) mainly involved in phytohormone metabolism, including ethylene, auxin, JA, and the <i>cis</i>-zeatin signal transduction pathway. There were also many DEGs involved in cell wall catabolism. Weighted gene co-expression network analysis (WGCNA) further suggested that the transcription factors <i>NAC100</i> and <i>ERF114</i> participate in the immature fruit abscission of <i>C. oleifera</i>. This study provides insights into the fruit abscission mechanism of <i>C. oleifera</i>.