ObjectiveCinnamoyl-CoA Reductase (CCR) is the first rate-limiting enzyme in the specific pathway for the synthesis of lignin and plays a crucial role in the biosynthesis of lignin. Measuring the lignin and monomer content of transgenic lines and wild lines (WT) aims to explore the effects of BpCCR1-sense and BpCCR1-antisense on the lignin of Betula platyphylla.

Method7-year-old BpCCR1-sense and BpCCR1-antisense transgenic lines were selected as experimental materials. The expression of BpCCR1 in transgenic lines was determined using PCR and qRT-PCR, respectively. The lignin content and monomer content were determined by the modified Klason method and high performance liquid chromatography (HPLC), respectively. The length and width of the wood fiber and basic density were measured by the method of nitric acid-potassium chlorate and drainage, and the height (H) and diameter at breast height (DBH) of the trees were investigated to investigate the effects of BpCCR1 sense and antisense lines in B. platyphylla.

ResultPCR analysis showed that the BpCCR1 was successfully integrated into the birch genome in 5 BpCCR1-sense transgenic lines and 14 BpCCR1-antisense transgenic lines. QRT-PCR analysis revealed that the expression of BpCCR1 was up-regulated in transgenic lines compared with wild type (WT). Lignin content of the transgenic lines was increased. There into, the average Klason lignin and total lignin content of 10 transgenic lines were respectively 7.46% and 7.05% higher than wild type. Compared with WT, FCR11 line had the highest content of average Klason lignin and total lignin, which was respectively increased by 12.26% and 11.81%. Although the wood basic density of transgenic lines had changed, while there was no obvious law. The wood fiber width of BpCCR1-sense transgenic lines was significantly smaller than WT, the average value of which decreased by 8.82% in five transgenic lines. Whereas, the wood fiber length of BpCCR1-antisense transgenic lines was restrained, and the difference between 11 lines and WT reached a significant level (P < 0.05), and the average value was 12.12% shorter than WT. The difference in volume between transgenic lines and WT also reached a significant level. The volume of 11 transgenic lines was larger than WT, and 7 lines reached a significant level, and the average volume growth was 77.1% higher than WT. FCR2, FCR27 and FCR32 lines were selected as excellent lines using principal component analysis.

ConclusionBoth the sense and antisense of BpCCR1 can increase the lignin content of B. platyphylla, three excellent transgenic lines were selected by six characters including height and DBH.