Abstract
BackgroundIn Arabidopsis, a long day flowering plant, CONSTANS (CO) acts as a transcriptional activator of flowering under long day (LD) condition. In rice, a short day flowering plant, Hd1, the ortholog of CO, plays dual functions in respond to day-length, activates flowering in short days and represses flowering in long days. In addition, alleles of Hd1 account for ~ 44% of the variation in flowering time observed in cultivated rice and sorghum. How does it work in bamboo? The function of CO in bamboo is similar to that in Arabidopsis?ResultsTwo CO homologous genes, PvCO1 and PvCO2, in Phyllostachys violascens were identified. Alignment analysis showed that the two PvCOLs had the highest sequence similarity to rice Hd1. Both PvCO1 and PvCO2 expressed in specific tissues, mainly in leaf. The PvCO1 gene had low expression before flowering, high expression during the flowering stage, and then declined to low expression again after flowering. In contrast, expression of PvCO2 was low during the flowering stage, but rapidly increased to a high level after flowering. The mRNA levels of both PvCOs exhibited a diurnal rhythm. Both PvCO1 and PvCO2 proteins were localized in nucleus of cells. PvCO1 could interact with PvGF14c protein which belonged to 14–3-3 gene family through B-box domain. Overexpression of PvCO1 in Arabidopsis significantly caused late flowering by reducing the expression of AtFT, whereas, transgenic plants overexpressing PvCO2 showed a similar flowering time with WT under LD conditions. Taken together, these results suggested that PvCO1 was involved in the flowering regulation, and PvCO2 may either not have a role in regulating flowering or act redundantly with other flowering regulators in Arabidopsis. Our data also indicated regulatory divergence between PvCOLs in Ph. violascens and CO in Arabidopsis as well as Hd1 in Oryza sativa. Our results will provide useful information for elucidating the regulatory mechanism of COLs involved in the flowering.ConclusionsUnlike to the CO gene in Arabidopsis, PvCO1 was a negative regulator of flowering in transgenic Arabidopsis under LD condition. It was likely that long period of vegetative growth of this bamboo species was related with the regulation of PvCO1.
Highlights
In Arabidopsis, a long day flowering plant, CONSTANS (CO) acts as a transcriptional activator of flowering under long day (LD) condition
Fifteen COL genes belonging to the COL gene family were obtained in this 31,987 functional annotation database
Another two genomic DNA sequences very similar to Hd1 were screened only in draft genome sequence, and these two complementary DNA (cDNA) or protein sequences were not found in 31,987 functional annotation database
Summary
In Arabidopsis, a long day flowering plant, CONSTANS (CO) acts as a transcriptional activator of flowering under long day (LD) condition. Some species have prolonged vegetative growth lasting decades before flowering and death One such species is Phyllostachys heterocycla, a woody bamboo that has ecological, economic and cultural value [4]. Another economically important species, Ph. violascens, belongs to the same genus and has very similar genetic background with Ph. heterocycla. Ph. violascens, belongs to the same genus and has very similar genetic background with Ph. heterocycla In this species, those elder plants at the age of 6 years would usually be harvested for gain yield of bamboo shoots. The CONSTANS (CO) gene was originally isolated as a photoperiodic floral promoter
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