Developmental responses of bread wheat to changes in ambient temperature following deletion of a locus that includes FLOWERING LOCUS T1

Abstract

FLOWERING LOCUS T (FT) is a central integrator of environmental signals that regulates the timing of vegetative to reproductive transition in flowering plants. In model plants, these environmental signals have been shown to include photoperiod, vernalization, and ambient temperature pathways, and in crop species, the integration of the ambient temperature pathway remains less well understood. In hexaploid wheat, at least 5 FT‐like genes have been identified, each with a copy on the A, B, and D genomes. Here, we report the characterization of FT‐B1 through analysis of FT‐B1 null and overexpression genotypes under different ambient temperature conditions. This analysis has identified that the FT‐B1 alleles perform differently under diverse environmental conditions; most notably, the FT‐B1 null produces an increase in spikelet and tiller number when grown at lower temperature conditions. Additionally, absence of FT‐B1 facilitates more rapid germination under both light and dark conditions. These results provide an opportunity to understand the FT‐dependent pathways that underpin key responses of wheat development to changes in ambient temperature. This is particularly important for wheat, for which development and grain productivity are sensitive to changes in temperature.

Zebularine treatment is associated with deletion of FT‐B1 leading to an increase in spikelet number in bread wheat

“…An independent deletion of FT-B1 was associated with a similar lateflowering phenotype (Dixon et al, 2018). These studies confirmed the importance of FT1 in promoting flowering in hexaploid wheat.…”

“…flowering; both wild type and the ft-b1 mutant flowered earlier at higher temperatures, although flowering was delayed at both temperatures in the mutant (Figure 7). High temperature acceleration of flowering was also observed in a deletion of FT-B1 that arose in a photoperiod-sensitive background (Dixon et al, 2018), where loss of ft-b1 delayed flowering to a similar extent at low or high temperatures.…”

“…We showed that FTB-1 plays a role in several stages of wheat development: Loss of FT-B1 enhanced dormancy (Figure 8); it delayed the transition to double ridge and so was associated with an increase in leaf number (Figure 4c,d); it slowed inflorescence development leading to an increase in spikelet number (Figure 2b,d; Dixon et al, 2018) and…”

CENTRORADIALIS Interacts with FLOWERING LOCUS T-Like Genes to Control Floret Development and Grain Number

“…Spikelet initiation occurs in the absence of FT1 expression, likely promoted by FT3. However, the timing of spikelet initiation is affected by variation in FT1 expression (Digel et al, 2015;Dixon et al, 2018).…”

Genetic pathways controlling inflorescence architecture and development in wheat and barley

“…Gain‐of‐function photoperiod‐insensitive alleles of Ppd‐1 were shown recently to reduce the number of spikelets that form on an inflorescence, which is caused by a shortened duration of early developmental stages that can be only partially compensated by an increased rate of spikelet initiation (Ochagavía et al ) (Figure ). Moreover, FT‐B1 ( FT1 from the B genome of bread wheat) acts downstream of Ppd‐1 to influence spikelet number, with loss of FT‐B1 resulting in increased spikelet number, in a thermally‐responsive manner (Dixon et al ; Finnegan et al ) (Figure ). FT1‐dependent control of spikelet architecture was also supported by recent analysis of TEOSINTE BRANCHED1 ( TB1 ; orthologue of Vrs5 ) function in wheat, which facilitates paired spikelet development, in a dosage dependent manner, by interacting with FT1 and reducing FT1‐dependent activation of spikelet meristem identity genes (Dixon et al ) (Figure ).…”