Exploration of Thiamin thiazole synthase (THI4) Expression and Transcriptomes Involved in the Floral Volatiles of Caladium bicolor

Abstract

4-methyl-5-vinylthiazole (MVT) is a significant volatile of caladium (Caladium bicolor) which produces a very high level of thiamin thiazole synthase (THI4) in male flowers. We explored transcriptomes upregulating MVT using RNA-seq during the six developmental stages of the male flower (Day−10 to Day0) in C. bicolor ‘Tapestry’. THI4 was the highest transcript throughout the male flower development. Additionally, the genes showing the high expression associated with floral volatiles of caladium on Day0 were trans-resveratrol di-O-methyltransferase (ROMT), chalcone synthase (CHS), 3-ketoacyl-CoA thiolase 2 (KAT2), and linalool synthase (TPS). These four genes correspond to the following elevated volatiles of caladium: 1,3,5-trimethoxybenzene, MVT, indole, methyl salicylate, and linalool on Day0 compared to Day−10. The upstream THI4 gene was cloned to drive a fluorescent gene (ZsGreen1) in transient and stable transgenic petunia and tobacco plants, showing the gene expression only in the male tissue. The tissue-specific expression of the caladium THI4 promoter could benefit crop production with minimal modification of plants. Investigating transcriptomes associated with caladium fragrance can help provide insight into understanding the regulatory mechanisms of floral volatiles of caladium.