Promoting flowering, lateral shoot outgrowth, leaf development, and flower abscission in tobacco plants overexpressing cotton FLOWERING LOCUS T (FT)-like gene GhFT1.

Chao Li,Xianzhong Huang,Yannan Zhang,Kun Zhang,Baiming Cui,Danli Guo,Xiyin Wang

doi:10.3389/fpls.2015.00454

Chao Li, Xianzhong Huang + Show 5 more

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https://doi.org/10.3389/fpls.2015.00454

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Abstract

FLOWERING LOCUS T (FT) encodes a mobile signal protein, recognized as major component of florigen, which has a central position in regulating flowering, and also plays important roles in various physiological aspects. A mode is recently emerging for the balance of indeterminate and determinate growth, which is controlled by the ratio of FT-like and TERMINAL FLOWER 1 (TFL1)-like gene activities, and has a strong influence on the floral transition and plant architecture. Orthologs of GhFT1 was previously isolated and characterized from Gossypium hirsutum. We demonstrated that ectopic overexpression of GhFT1 in tobacco, other than promoting flowering, promoted lateral shoot outgrowth at the base, induced more axillary bud at the axillae of rosette leaves, altered leaf morphology, increased chlorophyll content, had higher rate of photosynthesis and caused flowers abscission. Analysis of gene expression suggested that flower identity genes were significantly upregulated in transgenic plants. Further analysis of tobacco FT paralogs indicated that NtFT4, acting as flower inducer, was upregulated, whereas NtFT2 and NtFT3 as flower inhibitors were upregulated in transgenic plants under long-day conditions, but downregulated under short-day conditions. Our data suggests that sufficient level of transgenic cotton FT might disturb the balance of the endogenous tobacco FT paralogs of inducers and repressors and resulted in altered phenotype in transgenic tobacco, emphasizing the expanding roles of FT in regulating shoot architecture by advancing determine growth. Manipulating the ratio for indeterminate and determinate growth factors throughout FT-like and TFL1-like gene activity holds promise to improve plant architecture and enhance crop yield.

Highlights

Plants sense multiple environmental cues and endogenous signals to determine the appropriate timing of flowering, which is an orchestrated process through the integration of multiple environmental cues and endogenous signals
Cytoplasm and Nucleus Location of GhFT1 Protein We previously confirmed that GhFT1 located in the cytoplasm and nucleus by detecting the fused green fluorescence protein (GFP) in the Arabidopsis root cells carrying 35S::GhFT1-GFP (Guo et al, 2015)
We monitored the subcellular location of the GhFT1-GFP fusion protein by confocal lase scanning microscopy (CLSM) in the leaf epidermal cells of N. benthamiana

Summary

Introduction

Plants sense multiple environmental cues and endogenous signals to determine the appropriate timing of flowering, which is an orchestrated process through the integration of multiple environmental cues and endogenous signals. FT as well as TSF proteins including tomato SINGLE FLOWER TRUSS (SFT) and rice HEADING DATE 3a (Hd3a; Lifschitz et al, 2006; Corbesier et al, 2007; Mathieu et al, 2007; Tamaki et al, 2007; Notaguchi et al, 2008), nicknamed florigen, were produced in the phloem companion cells They are subsequently transported to the shoot apical meristem (SAM), where they form a complex involving a bZIP transcription factor FLOWERING LOCUS D (FD) to activate the expression of floral meristem identity genes, including SUPPRESSOR OF OVEREXPRESSION OF CONSTANS1 (SOC1), APETALA1 (AP1), and LEAFY (LFY; Abe et al, 2005; Wigge et al, 2005; Yoo et al, 2005; Kaufmann et al, 2010), which are important regulatory of hubs in the control of flowering time

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