Abstract
BackgroundFour-Coumarate:CoA ligase gene (4CL) plays multiple important roles in plant growth and development by catalyzing the formation of CoA ester. 4CL belongs to the plant phenylpropane derivative, which is related to the synthesis of flavonoids and lignin and is a key enzyme in the biosynthetic pathway.ResultsIn this study, 12 4CL genes of Fraxinus mandschurica were identified and named Fm4CL1-Fm4CL12, respectively. The analysis of the expression pattern of Fm4CL genes indicate that Fm4CL-like 1 gene may play a role in the lignin synthesis pathway. Our study indicate that overexpression of Fm4CL-like 1 increases the lignin content of transgenic tobacco by 39.5% compared to WT, and the S/G ratio of transgenic tobacco increased by 19.7% compared with WT. The xylem cell layer of transgenic line is increased by 40% compared to WT, the xylem cell wall thickness increased by 21.6% compared to the WT. Under mannitol-simulated drought stress, the root length of transgenic tobacco is 64% longer than WT, and the seed germination rate of the transgenic lines is 47% higher than that of WT. In addition, the H2O2 content in the transgenic tobacco was 22% lower than that of WT, while the POD and SOD content was higher than WT by 30 and 24% respectively, which showed Fm4CL-like 1 affect the accumulation of reactive oxygen species (ROS). The MDA content and relative conductivity was 25 and 15% lower than WT, respectively. The water loss rate is 16.7% lower than that of WT. The relative expression levels of stress-related genes NtHAK, NtAPX, NtCAT, NtABF2, and NtZFP were higher than those of WT under stress treatment. The stomatal apertures of OE (Overexpression) were 30% smaller than those of WT, and the photosynthetic rate of OE was 48% higher than that of WT. These results showed that the overexpression line exhibited stronger adaptability to osmotic stress than WT.ConclusionsOur results indicate that Fm4CL-like 1 is involved in secondary cell wall development and lignin synthesis. Fm4CL-like 1 play an important role in osmotic stress by affecting cell wall and stomatal development.
Highlights
Four-Coumarate:CoA ligase gene (4CL) plays multiple important roles in plant growth and development by catalyzing the formation of CoA ester. 4-coumarate: CoA ligase (4CL) belongs to the plant phenylpropane derivative, which is related to the synthesis of flavonoids and lignin and is a key enzyme in the biosynthetic pathway
Identification and phylogenetic analysis of 4CL from Fraxinus mandschurica We identified 12 4CL genes from the Fraxinus mandshurica transcriptome databases using the BioEdit local Blast method with 5 4CL genes of Arabidopsis thaliana and 3 4CL genes of Populus trichocarpa nucleotide sequences retrieved from National Center for Biotechnology Information (NCBI), named Fm4CL1Fm4CL12, which have all been uploaded to GenBank and assigned accession numbers (KJ531400- KJ531404, KF994781, KJ531405-KJ531410), characteristics of 12 Fm4CL gene sequences are in Additional file 1: Table S1
The lignin content in overexpression lines (OE) was approximately 39.5% higher than that in wild type (WT) (P < 0.05) (Fig. 4b), and the S/G ratio of transgenic tobacco increased by 19.7% compared with WT (P < 0.05)
Summary
Four-Coumarate:CoA ligase gene (4CL) plays multiple important roles in plant growth and development by catalyzing the formation of CoA ester. 4CL belongs to the plant phenylpropane derivative, which is related to the synthesis of flavonoids and lignin and is a key enzyme in the biosynthetic pathway. The xylem of the plant contains a large amount of lignin (about 25% of the woody part), mainly in the middle of the cellulose fiber. Lignin has several important functions for plants. (G-lignin) comprised of from guaiacylpropane structural monomers, and p-hydroxyphenyl lignin (H-lignin) comprised of p-hydroxy phenylpropane structural monomer [11]. The three kinds of lignin in nature do not occur in isolation in the plant, the gymnosperms mainly contain guaiacyl-based lignin (G); dicotyledons mainly have guaiacyl-lilac-based lignin (G-S); while monocots have conjugated Guajiba-lilacylp-hydroxyphenyl lignin (G-S-H) [11, 14, 15]. The activity and ratio of the different enzymes involved in lignin biosynthesis determine the type and rate of monomer synthesis and the proportion of each lignin monomer [16, 17]
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