The FT/FD‐dependent initiation of flowering under long‐day conditions in the day‐neutral species Nicotiana tabacum originates from the facultative short‐day ancestor Nicotiana tomentosiformis

Abstract

Photoperiod is an important external stimulus governing the precise timing of the floral transition in plants. Members of the FLOWERING LOCUS T (FT)-like clade of phosphatidylethanolamine-binding proteins induce this developmental process in numerous species by forming regulatory protein complexes with FD-like bZIP transcription factors. We identified several thus far unknown FT-like and FD-like genes in the genus Nicotiana and found that, even in the day-neutral species Nicotiana tabacum, floral initiation requires the photoperiod-dependent expression of several FT-like genes. Furthermore, floral promotion under long-day (LD) and short-day (SD) conditions is mediated by an FT-like protein (NtFT5) that originates from the genome of the paternal, facultative SD ancestor Nicotiana tomentosiformis. In contrast, its ortholog of the maternal LD ancestor Nicotiana sylvestris is not present in the genome of N. tabacum cv. SR1. Expression profiling in N. tabacum and its ancestors confirmed the relevance of these FT and FD orthologs in the context of polyploidization. We also found that floral inhibition by tobacco FT-like proteins is not restricted to SD conditions, highlighting the coincident expression of tobacco FT-like genes encoding floral activators and floral inhibitors. Multicolor bimolecular fluorescence complementation analysis revealed the preferential formation of FT/FD complexes that promote rather than inhibit flowering, which in concert with the regulation of NtFT and NtFD expression could explain how floral promotion overcomes floral repression during the floral transition in tobacco.

Mechanism of Allium Crops Bulb Enlargement in Response to Photoperiod: A Review

“…Attractively, the 35S:AcFT4 plants that do not bulb have a similar presence to leeks and sustain budding vegetatively into the winter, despite being deprived of their vegetation dying off. This recommends that the large phenotypic alterations between onion and leek might be due to an uncertain genetic variation [236][237][238][239][240][241]. Although the occurrence of enlarged bulbs is a distinct feature of onions, most members of the Allium genus produce some kind of storage organ.…”

The Major Floral Promoter NtFT5 in Tobacco (Nicotiana tabacum) Is a Promising Target for Crop Improvement

“…FT-like genes have been identified in several higher plant species, including important crops such as rice, sugar beet, potato, and tobacco (Kojima et al, 2002;Pin et al, 2010;Navarro et al, 2011;Harig et al, 2012;Beinecke et al, 2018). However, the influence of FT-like genes in these plants is not always limited to LD conditions.…”

Functional characterization of mungbean CONSTANS-LIKE genes reveals a key role for CONSTANS-LIKE 2 in the control of flowering time in A. thaliana under short-day conditions

“…Flowering time is a key factor that in uences crop growth and development, and crops achieve higher yields when they ower at the correct time. To regulate owering time, crops sense the interactions between endogenous and environmental factors to determinate the transition from vegetative to reproductive growth [1][2][3][4]. Several functional pathways have been identi ed that regulate the switch from vegetative to reproductive development.…”

“…These include the photoperiodic, vernalization, ambient temperature, plant hormone, and autonomous owering pathways [1,[4][5][6][7][8][9][10]. Within these pathways, a number of genes have been identi ed as involved in owering time regulation, including CONSTANS-LIKE (COL) genes, phosphatidyl ethanolamine-binding protein (PEBP) genes and several members of MADS-Box gene family [1][2][11][12][13][14][15][16][17][18][19].…”