Comparative transcriptome analysis of flower bud transition and functional characterization of EjAGL17 involved in regulating floral initiation in loquat

Abstract

Floral initiation plays a critical role for reproductive success in plants, especially fruit trees. However, little information is known on the mechanism of the initiation in loquat (Eriobotrya japonica Lindl.). Here, we used transcriptomic, expression and functional analysis to investigate the candidate genes in floral initiation in loquat. Comparative transcriptome analysis showed differentially expressed genes (DEGs) were mainly enriched in the metabolic pathways of plant hormone signal transduction. The DEGs were mainly involved in the gibberellin, auxin, cytokinin, abscisic acid, salicylic acid and ethylene signaling pathways. Meanwhile, some transcription factors, including MADS-box (MCM1, AGAMOUS, DEFI-CIENS and SRF), MYB (Myeloblastosis), TCP (TEOSINTE BRANCHED 1, CYCLOIDEA and PCF1), WOX (WUSCHEL-related homeobox) and WRKY (WRKY DNA-binding protein), were significantly differentially expressed. Among these key DEGs, we confirmed that an AGL17 ortholog EjAGL17 was significantly upregulated at the flower bud transition stage. Phylogenetic tree analysis revealed that EjAGL17 was grouped into an AGL17 clade of MADS-box transcription factors. Protein sequence alignment showed that EjAGL17 included a distinctive C-terminal domain. Subcellular localization of EjAGL17 was found only in the nucleus. Expression levels of EjAGL17 reached the highest at the development stage of flower bud transition. Moreover, ectopic expression of EjAGL17 in Arabidopsis significantly exhibited early flowering. Our study provides abundant resources of candidate genes for studying the mechanisms underlying the floral initiation in loquat and other Rosaceae species.

EjRAV1/2 Delay Flowering Through Transcriptional Repression of EjFTs and EjSOC1s in Loquat

“…The peculiar flowering habit of loquat ensures the availability of its fresh fruits in spring, a season short of fresh fruits in the market. Lots of endeavors aiming to identify pathways modulating flower induction in loquat have been carried out in the last decade (Esumi et al, 2005;Yang et al, 2007;Fernández et al, 2010;Liu et al, 2013;Zhang et al, 2016;Reig et al, 2017;Jiang et al, 2019Jiang et al, , 2020aChen W. et al, 2020;Xia et al, 2020). FT and SOC1 are floral integrators that link upstream photoperiod and other environmental or internal signals to promote flowering, while the downstream AP1 controls the identity of floral meristem during flower bud transition (Blümel et al, 2015;Bouché et al, 2016).…”

Genome-Wide Characterization of MADS-box Genes Identifies Candidates Associated with Flower and Fruit Development in Loquat (Eriobotrya japonica Lindl.)

“…The occurrence of double flowering in loquat was observed, with EjPI and EjAG playing key roles in these two double flowering phenomena, respectively [15,16]. In addition, in loquat, EjAGL17, EjAP1, and EjCAL were implicated in flower bud differentiation [17][18][19].…”

Sorbitol induces flower bud formation via the MADS‐box transcription factor EjCAL in loquat

“…Therefore, the flower bud induction period and blooming time affect the fruit yield and quality. Several genes related to flower development in cultivated loquat, such as EjLFY , EjAP1 , ( FLOWERING LOCUS T ) EjFT , EjSOC , EjTFL1 , and EjAGL17 , have been cloned (Esumi et al, 2005; Liu et al, 2013; Reig et al, 2017; Jiang et al, 2019; Jiang et al, 2020; Xia et al, 2020). EjTFL1‐1 and EjTFL1‐2 can inhibit FBD and promote the vegetative growth of loquat by integrating gibberellic acid (GA 3 ) and photoperiodic signals (Jiang et al, 2020).…”