Cloning and Functional Study of BlKNOX7 Gene in Betula luminifera
YU Qing1, HU Xiao-Qing2, ZHUANG He-Bi1, LIU Xue-Yu1, LIU Ming-Tong1, HUANG Hua-Hong1,*
1 National Key Laboratory for Development and Utilization of Forest Food Resources, Zhejiang A＆F University, Hangzhou 311300, China; 2 College of Ecology, Lishui University, Lishui 323000, China
Abstract：The KNOX (KNOTTED1-like homeobox gene) family serves as a core regulatory factor family for plant growth and development. Abnormal functions of this family can result in phenotypes such as organ malformations in plants. Therefore, analyzing its regulatory mechanism is of great significance for basic plant research and crop genetic improvement. In this study, the BlKNOX7 gene from Betula luminifera was cloned and its sequence characteristics were analyzed using bioinformatics methods. The expression patterns of the gene in various tissues and during tension wood formation were examined through qRT-PCR. Additionally, the phenotypic characteristics of transgenic Arabidopsis thaliana overexpressing BlKNOX7 were evaluated. The results showed that the BlKNOX7 gene (GenBank No. PV577094) consisted of 5 exons and 4 introns, with a cDNA sequence length of 1 095 bp and an ORF of 891 bp, encoding 296 amino acids. Evolutionary tree analysis revealed that BlKNOX7 clustered with the reported secondary wall development-associated transcription factor, Populus trichocarpa KNAT7. The expression of the BlKNOX7 gene in stems increased with the progress of lignification and reached the highest level in leaves. During the induction of tension wood, the expression level of BlKNOX7 in tension wood was significantly lower than that in the control. Overexpression of BlKNOX7 in Arabidopsis thaliana resulted in wavy curled plant leaves; Cross-sections of inflorescence stems stained with toluidine blue showed lighter coloration and a smaller range of coloration than the wild type, suggesting less lignin deposition. qRT-PCR results showed that BlKNOX7 overexpression significantly suppressed the expression of the Arabidopsis secondary wall synthesis pathway key enzyme genes phenylalanine ammonialyase (AtPAL)、 4-coumarate-COA ligase (At4CL)、irregular xylem (AtIRX) and cellulose synthase (AtCesA). This study provides a theoretical basis for further investigation of the molecular mechanisms of secondary wall development in Betula luminifera.
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