Abstract
The FLOWERING LOCUS T (FT) gene is a highly conserved florigen gene among flowering plants. Soybean genome encodes six homologs of FT, which display flowering activity in Arabidopsis thaliana. However, their contributions to flowering time in different soybean cultivars, especially in field conditions, are unclear. We employed six soybean cultivars with different maturities to extensively investigate expression patterns of GmFTLs (Glycine max FT-like) and GmCOLs (Glycine max CO-like) in the field conditions. The results show that GmFTL3 is an FT homolog with the highest transcript abundance in soybean, but other GmFTLs may also contribute to flower induction with different extents, because they have more or less similar expression patterns in developmental-, leaf-, and circadian-specific modes. And four GmCOL genes (GmCOL1/2/5/13) may confer to the expression of GmFTL genes. Artificial manipulation of GmFTL expression by transgenic strategy (overexpression and RNAi) results in a distinct change in soybean flowering time, indicating that GmFTLs not only impact on the control of flowering time, but have potential applications in the manipulation of photoperiodic adaptation in soybean. Additionally, transgenic plants show that GmFTLs play a role in formation of the first flowers and in vegetative growth.
Highlights
Photoperiod sensitivity is an important trait, which allows crops to adapt to diverse latitudinal environments for flowering and maturation at a suitable season
These data confirmed that the cultivars employed here were all photoperiodhyposensitive. To compare their flowering response to day length, six oybean cultivars were grown in a Harbin region, where the day length was about 16.5 hours during the growth season and shorter than that of their original locations (Fig 1), to make sure all cultivars can flower and mature normally.The results showed that early cultivars had three fully-opened trifoliolates when flowering, whereas middle and late ones had four trifoliolates
To investigate potential differences of different leaves in flowering induction, we harvested individual leaves according to developmental stages for real time quantitative PCR (RT-qPCR) analysis of genes, including GmFTLs, GmCOLs, and E genes
Summary
Photoperiod sensitivity is an important trait, which allows crops to adapt to diverse latitudinal environments for flowering and maturation at a suitable season. Many genes have been identified until now that are involved in the photoperiodic pathway of flowering. CONSTANS (CO) and FLOWERING LOCUS T (FT), form a central regulon (CO-FT) for flowering regulation [1]. The CO-FT regulon is a highly conserved module in many plants. PLOS ONE | DOI:10.1371/journal.pone.0136601 September 15, 2015
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