Transgenic overexpression of endogenous FLOWERING LOCUS T-like gene MeFT1 produces early flowering in cassava

Abstract

Endogenous FLOWERING LOCUS T homolog MeFT1 was transgenically overexpressed under control of a strong constitutive promoter in cassava cultivar 60444 to determine its role in regulation of flowering and as a potential tool to accelerate cassava breeding. Early profuse flowering was recorded in-vitro in all ten transgenic plant lines recovered, causing eight lines to die within 21 days of culture. The two surviving transgenic plant lines flowered early and profusely commencing as soon as 14 days after establishment in soil in the greenhouse. Both transgenic lines sustained early flowering across the vegetative propagation cycle, with first flowering recorded 30-50 days after planting stakes compared to 90 days for non-transgenic controls. Transgenic plant lines completed five flowering cycles within 200 days in the greenhouse as opposed to twice flowering event in the controls. Constitutive overexpression of MeFT1 generated fully mature male and female flowers and produced a bushy phenotype due to significantly increased flowering-induced branching. Flower induction by MeFT1 overexpression was not graft-transmissible and negatively affected storage root development. Accelerated flowering in transgenic plants was associated with significantly increased mRNA levels of MeFT1 and the three floral meristem identity genes MeAP1, MeLFY and MeSOC1 in shoot apical tissues. These findings imply that MeFT1 encodes flower induction and triggers flowering by recruiting downstream floral meristem identity genes. OPEN ACCESS Citation: Odipio J, Getu B, Chauhan RD, Alicai T, Bart R, Nusinow DA, et al. (2020) Transgenic overexpression of endogenous FLOWERING LOCUS T-like gene MeFT1 produces early flowering in cassava. PLoS ONE 15(1): e0227199.

Environmental responsiveness of flowering time in cassava genotypes and associated transcriptome changes

“…CC-BY 4.0 International license available under a (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made The copyright holder for this preprint this version posted February 12, 2021. ; https://doi.org/10.1101/2021.02.11.430817 doi: bioRxiv preprint expressed at higher levels in '0002 (early genotype) than in '419 (late genotype) while the over expression studies of MeFT1 by [15] further confirmed its florigenic properties. The role of FT as a mobile long distance signaling peptide that moves from leaf to shoot apical meristem to induce flowering has long been established in Arabidopsis [14,45].…”

“…The overexpression of Arabidopsis FT in cassava [4, 16] and of a native FT gene in cassava [15] resulted in significantly earlier flowering in late cassava genotypes. These early flowering phenotypes were accompanied by significantly reduced number of nodes to forking [4, 15], thus confirming that earliness is associated with a reduction number of nodes to fork type branching. Furthermore, [5] showed that the late-flowering genotype ‘419 initiates flowers at 22°C but not at warmer temperatures, which is in agreement with the current findings.…”

“…On the other hand, a cassava homolog Flowering Locus T (MeFT1), was generally expressed at higher levels before in Ubiaja than Ibadan. [5] first established that MeFT1 expression was related to flowering tendency as it was expressed at higher levels in ‘0002 (early genotype) than in ‘419 (late genotype) while the over expression studies of MeFT1 by [15] further confirmed its florigenic properties. The role of FT as a mobile long distance signaling peptide that moves from leaf to shoot apical meristem to induce flowering has long been established in Arabidopsis [14, 45].…”

“…The Flowering Locus T (FT) gene has been shown to be a flowering integrator of multiple flower inductive pathways and is positively correlated with flowering time in most species studied so far [14]. In cassava, as in many other species, the overexpression of the Arabidopsis FT gene and native cassava FT gene has been shown to accelerate flowering time in otherwise very late flowering genotypes [4, 15, 16]. This provides strong evidence for the involvement of FT in regulating also cassava flowering time.…”

Silver thiosulfate and Benzyladenine in combination with pruning additively feminizes cassava flowers and modulates transcriptome

“…Investigations into the reproductive biology of cassava has led to the development of several potential interventions to improve reproductive performance in cassava: transgenic intervention by overexpressing Flowering Locus FT (Adeyemo et al 2017;Odipio et al 2020;Bull et al 2017), modulating photoperiod and temperature to accelerate flowering time (Adeyemo et al 2019), application of silver thiosulfate to enhance flower development and longevity (STS) (Hyde et al 2020), or pruning young subtending branches to alleviate flower abortion (Pineda et al 2020). None so far has focused on increasing the proportion of female flowers.…”