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Abstract

A late-flowering transgenic radish has been produced by the expression of an antisense GIGANTEA (GI) gene fragment using a floral-dip method. Twenty-five plants were dipped into a suspension of Agrobacterium carrying a 2.5 kb antisense GI gene fragment from Arabidopsis, along with the gusA and bar reporter genes, all under the control of a CaMV 35S promoter. From a total of 1462 seeds harvested from these floral-dipped plants, 16 Basta-resistant T1 plants were found to have GUS activity (transformation efficiency of 1.1%). Southern analysis confirmed the integration of one or two copies of the gusA gene in these herbicide-resistant plants. Expression of the GI gene in T1 plants was much reduced compared to both wildtype plants and plants transformed with pCAMBIA3301 (positive control). In the progenies of eleven T1 plants analysed (T2 generation), all lines showed a significant delay in both bolting and flowering times compared to wildtype and positive control plants, and that, the level of GI transcript was inversely proportional to the time of bolting and flowering. At a maximum, bolting and flowering times were delayed by 17 and 18 days respectively, compared to wildtype plants (in positive control plants, the delay was 23 and 26 days, respectively). Ten of the 11 lines exhibited a significant reduction in plant height compared to wildtype and positive control plants. This study provides evidence that down-regulation of the GI gene by co-suppression could delay bolting in a cold-sensitive long-day (LD) plant. Production of late-flowering germplasms of radish may allow this important crop to be cultivated over an extended period and also provide further food to the famine countries of S/E Asia.

GIGANTEA – an emerging story

“…In another instance, expression of antisense AtGI gene, under the constitutive 35S promoter, led to delayed bolting in LDs, proving that GI has an important role in photoperiodic flowering time control in this plant ( Curtis et al, 2002 ). The bolting and flowering time was delayed by 17 and 18 days, respectively, with respect to WT plants.…”

Genome-wide identification and characterization of CONSTANS-like gene family in radish (Raphanus sativus)

“…These databases provide powerful tools for the genome-wide characterization of bolting and flowering genes in radish. Previous studies have reported a list of functional genes and microRNAs (miRNAs) related to radish bolting and flowering based on transcriptomic sequencing, expression profiling and transgenic approaches [ 2 , 28 , 29 ]. However, the specific biological and functional roles of the CO -like transcription factor genes in radish remain unknown.…”

De novo transcriptome analysis in radish (Raphanus sativus L.) and identification of critical genes involved in bolting and flowering

“…Moreover, some recent studies concerning the radish transcriptome assembly and analysis were reported, and a list of radish unique sequences were generated from various radish tissues [ 31 , 32 ]. Previous studies reported that several flowering genes have been isolated and characterized by expression profiling and transgenic approaches [ 33 – 35 ]. However, the genetic networks of bolting and flowering regulation in radish are poorly understood.…”