Expression patterns of flowering genes in leaves of ‘Pineapple’ sweet orange [Citrus sinensis (L.) Osbeck] and pummelo (Citrus grandis Osbeck)

Abstract

BackgroundIn citrus the transition from juvenility to mature phase is marked by the capability of a tree to flower and fruit consistently. The long period of juvenility in citrus severely impedes the use of genetic based strategies to improve fruit quality, disease resistance, and responses to abiotic environmental factors. One of the genes whose expression signals flower development in many plant species is FLOWERING LOCUS T (FT).ResultsIn this study, gene expression levels of flowering genes CiFT1, CiFT2 and CiFT3 were determined using reverse-transcription quantitative real-time PCR in citrus trees over a 1 year period in Florida. Distinct genotypes of citrus trees of different ages were used. In mature trees of pummelo (Citrus grandis Osbeck) and ‘Pineapple’ sweet orange (Citrus sinensis (L.) Osbeck) the expression of all three CiFT genes was coordinated and significantly higher in April, after flowering was over, regardless of whether they were in the greenhouse or in the field. Interestingly, immature ‘Pineapple’ seedlings showed significantly high levels of CiFT3 expression in April and June, while CiFT1 and CiFT2 were highest in June, and hence their expression induction was not simultaneous as in mature plants.ConclusionsIn mature citrus trees the induction of CiFTs expression in leaves occurs at the end of spring and after flowering has taken place suggesting it is not associated with dormancy interruption and further flower bud development but is probably involved with shoot apex differentiation and flower bud determination. CiFTs were also seasonally induced in immature seedlings, indicating that additional factors must be suppressing flowering induction and their expression has other functions.Electronic supplementary materialThe online version of this article (10.1186/s12870-017-1094-3) contains supplementary material, which is available to authorized users.

Rootstock Affects Floral Induction in Citrus Engaging the Expression of the FLOWERING LOCUS T (CiFT)

“…In kumquat and trifoliate orange, an increase in the expression levels of CiFT2 was observed during early summer, during (or just before) the onset of the flower organs [48]. Similar results were observed in pummelo (C. grandis Osbeck) and "Pineapple" sweet orange by Pajon et al [52], suggesting that the increase in CiFT gene expression soon after flowering is probably associated with changes in light conditions or internal signal regulation. Other factors could have played a role in the high expression levels recorded in July for TS/SC; among these are the increased solar radiation availability and the water-deficit stress induced by the very high evaporative demand during summer, even in irrigated plants.…”

The vascular targeted citrus FLOWERING LOCUS T3 gene promotes non-inductive early flowering in transgenic Carrizo rootstocks and grafted juvenile scions

“…Three FT homologs have been identified in the satsuma mandarin ( Citrus unshiu ). Among the three, the FT1 and FT2 are considered alleles at the same locus 26 , 27 , and therefore, only FT1 and FT3, was used in this study (Supplementary Fig. S1 ).…”

Genome-wide identification and characterization of flowering genes in Citrus sinensis (L.) Osbeck: a comparison among C. Medica L., C. Reticulata Blanco, C. Grandis (L.) Osbeck and C. Clementina

“…They observed that the expression level of three genes was at peak during the month of April and subsided after that regardless of the conditions in which they were growing (protected or open field conditions). In C. unshiu , three FT transcripts, CiFT1 , CiFT2 , and CiFT3 have been identified and characterized [ 75 , 162 ] of which CiFT1 and CiFT2 are isoforms encoded by the same gene [ 163 ] and CiFT3 is considered a better floral-inductive treatment compared to CiFT1 and CiFT2 [ 164 , 165 ]. Soares et al [ 108 ] developed transgenic “Carrizo” citrange hybrid using CcFT1 and CcFT3 (homologs of FT in C. clementine ).…”