Bud sprouting and floral induction and expression of FT in loquat [Eriobotrya japonica (Thunb.) Lindl.]

Abstract

EjFT1 and EjFT2 genes were isolated and sequenced from leaves of loquat. EjFT1 is involved in bud sprouting and leaf development, and EjFT2 in floral bud induction. Loquat [Eriobotrya japonica (Thunb.) Lindl.] is an evergreen species belonging to the family Rosaceae, such as apple and pear, whose reproductive development, in contrast with these species, is a continuous process that is not interrupted by winter dormancy. Thus, the study of the mechanism of flowering in loquat has the potential to uncover the environmental and genetic networks that trigger flowering more accurately, contributing for a better understanding of the Rosaceae floral process. As a first step toward understanding the molecular mechanisms controlling flowering, extensive defoliation and defruiting assays, together with molecular studies of the key FLOWERING LOCUS T (FT) gene, were carried out. FT exhibited two peaks of expression in leaves, the first one in early to mid-May, the second one in mid-June. Two FT genes, EjFT1 and EjFT2, were isolated and sequenced and studied their expression. Expression of EjFT1 and EjFT2 peaks in mid-May, at bud sprouting. EjFT2 expression peaks again in mid-June, coinciding with the floral bud inductive period. Thus, when all leaves of the tree were continuously removed from early to late May vegetative apex differentiated into panicle, but when defoliation was performed from early to late June apex did not differentiate. On the other hand, fruit removal advanced EjFT1 expression in old leaves and the sooner the fruit detached, the sooner the bud sprouted. Accordingly, results strongly suggest that EjFT1 might be related to bud sprouting and leaf development, while EjFT2 might be involved in floral bud induction. An integrative model for FT functions in loquat is discussed.

The Role of EjSPL3, EjSPL4, EjSPL5, and EjSPL9 in Regulating Flowering in Loquat (Eriobotrya japonica Lindl.)

“…Silencing this gene led to down-regulation of cmo-miR156 and up-regulation of CmSPL3, CmSPL5, and CmSPL9 [58]. Interestingly, EjFT2 showed involvement in the process of flower bud differentiation in loquat [62]. In order to ascertain whether there is a similar pattern of flowering regulation in the EjSPL genes in loquat, we need more in-depth research.…”

Modulation of Dormancy and Growth Responses in Reproductive Buds of Temperate Trees

“…The proposed functions of FT1 in flower induction and dormancy release and FT2 in the regulation of photoperiodic growth cessation in poplar constitute a paradigmatic case of neo-functionalization after a gene duplication event in trees, in contrast to the main role of FT in the transition to flowering in Arabidopsis ( Pin and Nilsson, 2012 ). A role for FT and the similar but functionally antagonist TFL genes in flower induction has been also postulated in other perennial species different from poplar, based on expression and transgenic studies ( Kotoda and Wada, 2005 ; Jones et al, 2011 ; Ziv et al, 2014 ; Bai et al, 2017 ; Reig et al, 2017 ). Similarly, orthologs of Arabidopsis flowering genes LEAFY ( LFY ) and AP1 perform a function related to flowering transition in perennial species.…”

EjFRI, FRIGIDA (FRI) Ortholog from Eriobotrya japonica, Delays Flowering in Arabidopsis

“…Unlike other Rosaceae plants [38][39][40][41][42][43], which lived through winters for flowering in springs, the flowering of cultivated loquat is not blocked, and they will bloom in late-autumn or winter. In woody perennials, shoot meristem displays transitions between vegetative and reproductive development [8]. We assumed that EjFRI may play a different role during this transition because of the exceptional flowering character of cultivated loquat.…”

“…In Arabidopsis, almost 180 genes have been illuminated in flowering-time control based on the analyses of transgenic plants and loss-of-function mutations [2]. To date, some regulatory genes of flowering time have been isolated and characterized from loquat, including EjSOC1, EjFT, EjFD, EjGI, EjSVP, EjCO, EjAP1, EjTFL1 and EjLEY [3][4][5][6][7][8][9]. Among these genes, orthologous genes of the floral integrators, such as EjFT and EjSOC1, are identified and reported to regulate plant flowering-time by adjusting the environmental…”