Functional Analysis of OfbHLH89 Gene in Regulating Flower Opening in Osmanthus fragrans
The flower opening process was investigated by screening and cloning gene OfbHLH89 from the Osmanthus fragrans transcriptome database.This gene has a coding frame(ORF)that is 744 bp long and encodes for 247 amino acids.Sequence alignment and phylogenetic tree analysis revealed that OfbHLH89 shared similarities of 54.1％and 52.74％with Vigna angularis VaBPE and Capsicum baccatum CbBPE,respectively.The subcellular localization results showed that OfbHLH89 was localized on the nucleus.Spatiotemporal expression analysis showed that OfbHLH89 was highly expressed in the flower,and its expression gradually increased from ball-shaped stage to full flowering stage,reaching a peak at the full flowering stage.Further analysis revealed that under low temperature induction,the relative expression level of OfbHLH89 in the flower buds was significantly higher than that of the control.In Petunia hybrida,overexpression of OfbHLH89 resulted in the enlargement of petals,suggesting that OfbHLH89 may be involved in petal expansion during flower opening in O.fragrans.Additionally,the expression of PhEXPA1,PhXTH24,and PhXTH25 were significantly up-regulated.Quantitative analysis of downstream cell expansion related genes by transient transformation of OfbHLH89 into O.fragrans flower buds revealed that the expression of OfXTH5,OfXTH21,OfXTH32,OfXTH34,OfEXPA4 and OfEXPA13 were significantly upregulated compared with empty vector.It is suggested that OfbHLH89 can impact the flower opening of O.fragrans by activating the transcription of genes related to cell expansion,leading to increase in petal size.
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