Functional Characteristics of Caffeoyl Shikimate Esterase in Larix Kaempferi and Monolignol Biosynthesis in Gymnosperms
1
College of Biological Sciences and Biotechnology, Beijing Forestry University, Beijing 100083, China
2
National Engineering Laboratory for Tree Breeding, the Tree and Ornamental Plant Breeding and Biotechnology Laboratory of Chinese Forestry Administration, Beijing 100083, China
*
Author to whom correspondence should be addressed.
Int. J. Mol. Sci. 2019, 20(23), 6071; https://doi.org/10.3390/ijms20236071
Received: 28 October 2019 / Revised: 19 November 2019 / Accepted: 26 November 2019 / Published: 2 December 2019
(This article belongs to the Special Issue Woody Formation and Lignin Biosynthesis in Plants)
Caffeoyl shikimate esterase (CSE) has been reported to be involved in lignin biosynthesis; however, studies of CSE in gymnosperms are lacking. In this study, CSE was successfully cloned from Larix kaempferi (LkCSE) based on Larix laricina transcriptome screening. LkCSE was likely to have catalytic activity based on homologous sequence alignment and phylogenetic analyses of CSEs from different species. In vitro assays with the recombinant enzyme validated the catalytic activity of LkCSE, indicating its function in converting caffeoyl shikimate into caffeate and shikimate. Additionally, the optimum reaction pH and temperature of LkCSE were determined to be 6.0 and 30 °C, respectively. The values of Km and Vmax of CSE for caffeoyl shikimate were 98.11 μM and 14.44 nM min−1, respectively. Moreover, LkCSE was observed to have tissue expression specificity and was abundantly expressed in stems and leaves, especially stems, which was 50 times higher than the expression levels of roots. Lastly, translational fusion assays using LkCSE fused with green fluorescent proteins (GFP) in tobacco leaves indicated that LkCSE was localized in the plasma membrane and endoplasmic reticulum (ER). These results revealed that CSE clearly functions in gymnosperms and it is possible for LkCSE to interact with other ER-resident proteins and regulate mass flux in the monolignol biosynthesis pathway.
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Wang, X.; Chao, N.; Zhang, M.; Jiang, X.; Gai, Y. Functional Characteristics of Caffeoyl Shikimate Esterase in Larix Kaempferi and Monolignol Biosynthesis in Gymnosperms. Int. J. Mol. Sci. 2019, 20, 6071.
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