UDP-glycosyltransferase 72B1 catalyzes the glucose conjugation of monolignols and is essential for the normal cell wall lignification in Arabidopsis thaliana.
Glycosylation of monolignols has been found to be widespread in land plants since the 1970s. However, whether monolignol glycosylation is crucial for cell wall lignification and how it exerts effects are still unknown. Here, we report the identification of a mutant ugt72b1 showing aggravated and ectopic lignification in floral stems along with arrested growth and anthocyanin accumulation. Histochemical assays and thioacidolysis analysis confirmed the enhanced lignification and increased lignin biosynthesis in the ugt72b1 mutant. The loss of UDP-glycosyltransferase UGT72B1 function was responsible for the lignification phenotype, as demonstrated by complementation experiments. Enzyme activity analysis indicated that UGT72B1 could catalyze the glucose conjugation of monolignols, especially coniferyl alcohol and coniferyl aldehyde, which was confirmed by analyzing monolignol glucosides of UGT72B1 transgenic plants. Furthermore, the UGT72B1 gene was strongly expressed in young stem tissues, especially xylem tissues. However, UGT72B1 paralogs, such as UGT72B2 and UGT72B3, had weak enzyme activity toward monolignols and weak expression in stem tissues. Transcriptomic profiling showed that UGT72B1 knockout resulted in extensively increased transcript levels of genes involved in monolignol biosynthesis, lignin polymerization and cell wall-related transcription factors, which was confirmed by quantitative real-time PCR assays. These results provided evidence that monolignol glucosylation catalyzed by UGT72B1 was essential for normal cell wall lignification, thus offering insight into the molecular mechanism of cell wall development and cell wall lignification.
Key Laboratory of Plant Cell Engineering and Germplasm Innovation, Ministry of Education of China, School of Life Sciences, Shandong University, Jinan, 250100, China.
Ji-Shan
JS
Lin
Key Laboratory of Plant Cell Engineering and Germplasm Innovation, Ministry of Education of China, School of Life Sciences, Shandong University, Jinan, 250100, China.
Xu-Xu
XX
Huang
Key Laboratory of Plant Cell Engineering and Germplasm Innovation, Ministry of Education of China, School of Life Sciences, Shandong University, Jinan, 250100, China.
Qin
Q
Li
Key Laboratory of Biofuels, Qingdao Engineering Research Center of Biomass Resources and Environment, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, 266101, China.
Yingping
Y
Cao
Key Laboratory of Biofuels, Qingdao Engineering Research Center of Biomass Resources and Environment, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, 266101, China.
Yan
Y
Bao
Key Laboratory of Plant Cell Engineering and Germplasm Innovation, Ministry of Education of China, School of Life Sciences, Shandong University, Jinan, 250100, China.
Xia-Fei
XF
Meng
Key Laboratory of Plant Cell Engineering and Germplasm Innovation, Ministry of Education of China, School of Life Sciences, Shandong University, Jinan, 250100, China.
Yan-Jie
YJ
Li
Key Laboratory of Biofuels, Qingdao Engineering Research Center of Biomass Resources and Environment, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, 266101, China.
Chunxiang
C
Fu
Key Laboratory of Plant Cell Engineering and Germplasm Innovation, Ministry of Education of China, School of Life Sciences, Shandong University, Jinan, 250100, China. bkhou@sdu.edu.cn.
Bing-Kai
BK
Hou
D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002473:Cell Wall / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism*; D016695:Glycosyltransferases / Q000235:genetics / Q000378:metabolism*; D008031:Lignin / Q000378:metabolism*
D029681:Arabidopsis Proteins; D008031:Lignin; D016695:Glycosyltransferases; D005947:Glucose

Arabidopsis thaliana
; cell wall; glycosylation; glycosyltransferase; lignification; monolignols; transcriptome