The MADS-Box Gene SlMBP21 Regulates Sepal Size Mediated by Ethylene and Auxin in Tomato

Abstract

Normal organ size is achieved by successful co-ordination of cell proliferation and cell expansion, which are modulated by multiple factors such as ethylene and auxin. In our work, SlMBP21-RNAi (RNA interference) tomato exhibited longer sepals and improved fruit set. Histological analysis indicated that longer sepals were attributed to cell expansion. To explore how SlMBP21 regulates sepal size, we compared the transcriptomes of sepals between SlMBP21-RNAi and the wild type by RNA sequencing and found that the differentially expressed genes were dominantly related to cell expansion, ethylene and auxin, and photosynthesis. Down-regulation of SlMBP21 affected ethylene production and the free IAA and IAA-Val intensity in sepals. Hormone treatment further indicated that SlMBP21 was involved in the ethylene and auxin pathways. As reported, ethylene and auxin were important factors for cell expansion. Hence, SlMBP21 negatively regulated cell expansion to control sepal size, and ethylene and auxin may mediate this process. Additionally, the contents of Chl and the activity of ribulose-1, 5-bisphosphate carboxylase/oxygenase, the key photosynthetic enzyme, were both increased in SlMBP21-RNAi sepals, which indicated that photosynthesis might be enhanced in transgenic longer sepals. Therefore, the longer sepal, with better protection and enhanced photosynthesis, may contribute to improve fruit set. Altogether, these results suggested that SlMBP21 was a novel factor involved in organ size control. Moreover, our study provided potential application value for improving fruit set.

Comparative Transcriptomic Analysis of the Development of Sepal Morphology in Tomato (Solanum Lycopersicum L.)

“…Among the green parts of the flower, sepal has the greatest ability to photosynthesis, follow by the receptacle [3]. The contents of Chl and the activity of ribulose-1, 5-bisphosphate carboxylase/oxygenase, the key photosynthetic enzyme, are both increased in longer sepals, and photosynthesis is enhanced in longer sepals, which may contribute by improving the fruit set [2]. Conclusively, sepal morphology is closely associated with fruit development.…”

“…The larger sepal size tightly associates with the protection of flower whorl and better fruit quality [1]. In SlMBP21-RNAi tomato, the sepals are longer and fruit sets are improved [2]. Among the green parts of the flower, sepal has the greatest ability to photosynthesis, follow by the receptacle [3].…”

“…The overexpression of another MADS-box gene, namely SlFYFL, gives rise to longer sepals [16]. The MADS-box gene SlMBP21 regulates the development of sepals and the floral abscission zone [2,17,18]. Moreover, the SEPALLATA (E-function) MADS-box gene SlCMB1 participates in the development of inflorescence architecture and also regulates sepal size in tomato plants [19].…”

“…"ARF" in the red box indicates the one ARF gene (Solyc04g081240.2). "AUX/IAA" in the green box represents the seven AUX/IAA genes (Solyc06g008590.2, Solyc08g021820 2,. Solyc09g083290.2, Solyc09g090910.1, Solyc04g076850.2, Solyc06g053830.2, Solyc06g053840.2).…”

Suppression of SlMBP15 Inhibits Plant Vegetative Growth and Delays Fruit Ripening in Tomato

“…Furthermore, TM8 overexpression in tomato plants generated anomalous stamens with poorly viable pollen ( Daminato et al, 2014 ). A recent study suggested the tomato MADS-box gene SlMBP21 is a novel factor involved in organ size control ( Li et al, 2017 ).…”