Conservation of Arabidopsis thaliana Photoperiodic Flowering Time Genes in Onion (Allium cepa L.)

Abstract

The genetics underlying onion development are poorly understood. Here the characterization of onion homologs of Arabidopsis photoperiodic flowering pathway genes is reported with the end goal of accelerating onion breeding programs by understanding the genetic basis of adaptation to different latitudes. The expression of onion GI, FKF1 and ZTL homologs under short day (SD) and long day (LD) conditions was examined using quantitative reverse transcription-PCR (qRT-PCR). The expression of AcGI and AcFKF1 was examined in onion varieties which exhibit different daylength responses. Phylogenetic trees were constructed to confirm the identity of the homologs. AcGI and AcFKF1 showed diurnal expression patterns similar to their Arabidopsis counterparts, while AcZTL was found to be constitutively expressed. AcGI showed similar expression patterns in varieties which exhibit different daylength responses, whereas AcFKF1 showed differences. It is proposed that these differences could contribute to the different daylength responses in these varieties. Phylogenetic analyses showed that all the genes isolated are very closely related to their proposed homologs. The results presented here show that key genes controlling photoperiodic flowering in Arabidopsis are conserved in onion, and a role for these genes in the photoperiodic control of bulb initiation is predicted. This theory is supported by expression and phylogenetic data.

FLOWERING LOCUS T genes control onion bulb formation and flowering

“…For example, LD onions are grown in temperate regions where bulbing is initiated once the daylength reaches at least 16 h per day, whereas short-day (SD) onions are grown in more tropical regions and require a daylength of only 12 h for bulbing 1 . This photoperiodic initiation of bulbing resembles the photoperiodic flowering in other plants 21,22 . As with flowering, daylength perception probably occurs in the leaves, while the response is in the meristem 1 , suggesting a mobile signal with properties similar to FT might be involved.…”

Putative sugarcane FT/TFL1 genes delay flowering time and alter reproductive architecture in Arabidopsis

“…ScTFL1 sequence is more similar to the rice and maize homologs compared to Arabidopsis (Figure 1D). The founding member of this family, Arabidopsis TFL1 , is highly conserved between species, and homologs have been reported in several different species (Hecht et al, 2005; Danilevskaya et al, 2010; Taylor et al, 2010; Mauro-Herrera et al, 2013). …”

Structure and Function of the ZTL/FKF1/LKP2 Group Proteins in Arabidopsis

“…To more accurately access the function of the in vivo interactions of the members, it would be better to use systems that resemble endogenous conditions. Since ZTL group family-related genes are conserved not only in angiosperms (both monocots and dicots) [89], but also in the lycophyte Selaginella moellendorffii [90], it is likely that this protein family plays an important role in all vascular plants. Selaginella has only one ZTL homolog [90].…”