Molecular analysis of a homogentisate phytyltransferase gene from Lactuca sativa L

Tocochromanols, usually known as vitamin E, play a crucial role in human and animal nutrition. The enzyme homogentisate phytyltransferase (HPT) performs the first committed step of the vitamin E biosynthetic pathway. The full-length cDNA encoding HPT was isolated from Lactuca sativa L. by rapid amplification of cDNA ends (RACE). The cDNA, designated as LsHPT, was 1,670 bp long containing an open reading frame (ORF) of 1,185 bp which encoded a protein of 395 amino acids. Sequence analysis indicated that the deduced protein, named as LsHPT, shared high identity with other dicotyledonous HPTs. Real-time fluorescent quantitative PCR (qPCR) analysis revealed that LsHPT was preferentially expressed in mature leaves compared with other tissues. When lettuce plants were subjected to drought and high-light stress treatments, LsHPT expression was markedly increased. Expression of LsHPT in Arabidopsis showed that LsHPT could enhance the α-tocopherol biosynthesis in Arabidopsis. Transient expression of LsHPT via agroinfiltration resulted in 9-fold increase in LsHPT mRNA level and nearly 18-fold enhancement in α-tocopherol content compared with the negative controls.