Introduction to Physical Systems Modelling with Bond Graphs

Abstract

As a typical climacteric fruit, tomato (<i>Solanum lycopersicum</i>) is widely used for studying the ripening process. The negative regulation of tomato fruits by transcription factor <i>SlNAC1</i> has been reported, but its regulatory network was unclear. In the present study, we screened a transcription factor, <i>SlERF109-like</i>, and found it had a stronger relationship with <i>SlNAC1</i> at the early stage of tomato fruit development through the use of transcriptome data, RT-qPCR, and correlation analysis. We inferred that SlERF109-like could interact with SlNAC1 to become a regulatory complex that co-regulates the tomato fruit ripening process. Results of transient silencing (VIGS) and transient overexpression showed that <i>SlERF109-like</i> and <i>SlNAC1</i> could regulate chlorophyll degradation-related genes (<i>NYC1</i>, <i>PAO</i>, <i>PPH</i>, <i>SGR1</i>), carotenoids accumulation-related genes (<i>PSY1</i>, <i>PDS</i>, <i>ZDS</i>), ETH-related genes (<i>ACO1</i>, <i>E4</i>, <i>E8</i>), and cell wall metabolism-related genes expression levels (<i>CEL2</i>, <i>EXP</i>, <i>PG</i>, <i>TBG4</i>, <i>XTH5</i>) to inhibit tomato fruit ripening. A dual-luciferase reporter and yeast one-hybrid (Y1H) showed that SlNAC1 could bind to the <i>SlACO1</i> promoter, but SlERF109-like could not. Furthermore, SlERF109-like could interact with SlNAC1 to increase the transcription for <i>ACO1</i> by a yeast two-hybrid (Y2H) assay, a luciferase complementation assay, and a dual-luciferase reporter. A correlation analysis showed that <i>SlERF109-like</i> and <i>SlNAC1</i> were positively correlated with chlorophyll contents, and negatively correlated with carotenoid content and ripening-related genes. Thus, we provide a model in which SlERF109-like could interact with SlNAC1 to become a regulatory complex that negatively regulates the tomato ripening process by inhibiting <i>SlACO1</i> expression. Our study provided a new regulatory network of tomato fruit ripening and effectively reduced the waste of resources.