Tomato (Solanum lycopersicum) has the advantages of small genome, short growth cycle, self-pollination, obvious fruit development characteristics, and mature transformation system. It has become an important model plant for fruit (including fruits and vegetables) research; at the same time, tomato It is also favored by consumers as a fruit or vegetable and has important economic value. However, the characteristics of tomato flower and fruit drop have a significant correlation with the yield. It is of great significance to reduce flower and fruit drop and increase tomato yield in production practice.
Recently, Horticulture Research published a research paper entitled Tomato SlBL4 plays an important role in fruit pedicel organogenesis and abscission online by the team of Hada and Yanfang of Inner Mongolia University and the team of Li Zhengguo of Chongqing University.
BELL subfamily contains a small TALE homology structure box, which exists in all terrestrial plants and plays an important role in the growth and development of plants. The preliminary research of this project found that down-regulating tomato SlBL4 makes tomato fruits appear darker green, chlorophyll content increases, and sugar accumulation increases; further RNA-seq and ChIP-seq analysis found that SlBL4 participates in chlorophyll accumulation, chloroplast development, and cell wall during tomato fruit ripening. Metabolism and carotenoid accumulation (Yan et al. 2020).
This study further showed that after the SlBL4 gene was disturbed in tomato, the pedicle stalks of the transgenic plants were enlarged and the fruit shed early. The stalk separation of SlBL4 was analyzed two days before tomato flowering, the day of flowering, and 2 days after flowering. The regional expression pattern found that the expression level of SlBL4 gradually increased with the increase of the number of flowering days. It is speculated that SlBL4 plays an important role in the process of tomato stalk enlargement and early fruit shedding.
Further studies on the function of SlBL4 found that combined with microscopic techniques such as paraffin sectioning, resin sectioning and projection electron microscopy, the cells in the pedicel separation zone of the SlBL4 interference strain disappeared, the epidermal cell layer increased significantly and the cell diameter increased; the study also Through RNA-seq analysis, the differentially expressed genes related to apical meristems, auxin transport and signal transduction, and cell wall metabolism were screened; combined with ChIP-seq results and dual luciferase experiments:it showed that SlBL4 protein can activate the transcription factor JOINTLESS, OVATE and auxin transport-related genes PIN1 and LAX3 then regulate the formation and shedding of the tomato aerospace zone.
In summary, this study laid the foundation for clarifying the function of SlBL4 in plants, and has important reference value for the regulation mechanism of fruit stalk development and shedding. The research results can lay a theoretical foundation for in-depth elucidation of the complex regulatory network of fruit stalk development and shedding.
Dr. Yan Fang from Inner Mongolia University is the first author, Professor Hada and Professor Li Zhengguo are the corresponding authors. Professor Deng Wei, Hu Guojian and Dr. Zhang Qiang, graduate students Gong Zhehao, Ma Xuesong, Yu Ruonan and Bai Runyao participated in some of the work.
This research was funded by the National Natural Science Foundation of China and the High-level Talent Introduction Project of Inner Mongolia University.
References:Yan F, Gao Y, Pang X, Xu X, Zhu N, Chan H, Hu G, Wu M, Yuan Y, Li H, Zhong S, Hada W, Deng Wei*, Li ZG* ( 2020) SlBL4 regulates chlorophyll accumulation, chloroplast development and cell wall metabolism in tomato fruit. Journal of Experimental Botany doi.org/10.1093/jxb/eraa272
Fig. 4 The fruit-dropping phenotypes of the SlBL4 RNAi plants.