SLGT11 Controls Floral Organ Patterning and Floral Meristem Termination in Tomato

Abstract

Background: Flower development affects fruit production directly in tomato. Despite the framework mediated by ABC genes have been established in Arabidopsis, the spatiotemporal precision of floral development in tomato has not been well examined.Results: Here, we analyzed a novel tomato mutant in which the normal development of stamens and carpels failed, resulting in ectopic formation of floral and shoot apical meristem in the fourth whorl position, which later developed into stem-and leaf-like structures. Using bulked segregant analysis (BSA), we assigned the causal mutation to the gene SLGT11 that encodes a transcription factor belonging to Trihelix gene family. Further RNAi silencing of SLGT11 verified the defective phenotypes of slf mutant. The failed termination of floral meristem and the occurrence of floral reversion in slf mutant indicate that SLGT11 functions as a non-canonical C type gene. Furthermore, we found that the defects in slf were substantially enhanced at higher temperature, with petals transformed into sepals, all stamens disappeared, and increased frequency of ectopic floral meristem. Conclusions: Together with the spatiotemporal expression pattern, we suggest that SLGT11 functions in floral organ patterning and termination of floral meristem identity in tomato. Arabidopsis, the activity of floral meristem is maintained through the WUSCHEL-CLAVATA (WUS-CLV) signaling pathway until carpel primordial is initiated [1]. In later stage of flower development (starting from stage), AGAMOUS (AG) represses WUS through activating KNUCKLES (KNU) directly in floral meristem to ensure the correct progression of further floral development [2, 3]. A large number of regulators such as PAN, ULT1, RBL, SQN, SUP, SEP3, ARF3, MIF and CRC, participate in floral regulation by direct or indirect regulation of WUS activity [4-13]. These regulators form the complex network interplaying with plant hormones during the floral development. It was found that ARF3 is regulated by auxin, AG and AP2 in developing flowers, which represses cytokinin activity to inhibit 3 WUS [14]. The mechanisms of floral development could also be conserved among species. For example, it was found KNU interacts with MIF to regulate WUS expression and this mechanism is conservative between Arabidopsis and tomato [12]. Flower reversion is an unusual process in which the committed flower development is reverted back to vegetative growth, resulting in outgrowth of leaf or inflorescence structures emerged from the first flower [1]. This phenomenon is often related to varied environmental conditions, such as temperature and photoperiod. For example, such floral reversion was observed in lfy-6 and ag-1 mutants of Arabidopsis grown in short days [15]. Besides over expression of AGL24 also causes ectopic inflorescence development [16]. Floral reversion was also observed in the natural allopolyploid Arabidopsis suecica, in which abnormal expression of floral genes, including AGL24, AP1, SVP and SOC1 was detected [17, 18]. Unlike Arabidopsis, LFY, TFL1...