AUTHOR=Wang Han , Zhang Yingjie , Feng Xiaofeng , Peng Fulei , Mazoor Muhammad Aamir , Zhang Yang , Zhao Yu , Han WenLong , Lu Jinjin , Cao Yunpeng , Cai Yongping 

TITLE=Analysis of the β-Glucosidase Family Reveals Genes Involved in the Lignification of Stone Cells in Chinese White Pear (Pyrus bretschneideri Rehd.)

JOURNAL=Frontiers in Plant Science

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2022.852001

DOI=10.3389/fpls.2022.852001

ISSN=1664-462X

ABSTRACT=<p>BGLU β-glucosidases in glycoside hydrolase family 1 (GH1) are involved in many processes of plant secondary metabolism. In particular, its de-glycosylation function plays an important role in the transport of lignin monolignols. No comprehensive study of the BGLU family in Chinese pear (<italic>Pyrus bretschneideri</italic> Rehd.) has been reported yet. In this study, the 50 BGLU family members from Chinese white pear were identified. Three candidate genes, <italic>PbBGLU1</italic>, <italic>PbBGLU15</italic>, and <italic>PbBGLU16</italic>, that may be involved in lignin synthesis were screened by bioinformatics analysis and qRT-PCR. Subcellular localization showed that all three of these candidate genes were expressed in the extracellular region. Then, we analyzed the functions of <italic>PbBGLU1</italic> and <italic>PbBGLU16. In situ</italic> hybridization analysis showed that <italic>PbBGLU1</italic> transcripts were not only localized to some pulp cell walls, lignin deposition, and stone cell areas of a pear fruit, but that was also a small amount of enrichment in normal pear flesh cells. <italic>PbBGLU16</italic> transcripts were only enriched in lignin deposition and stone cell areas of pear fruit. Enzyme activity analysis revealed that GST-PbBGLU1 and GST-PbBGLU16 had a stronger activity and higher catalytic efficiency for coniferin than syringin. In addition, GST-PbBGLU16 exhibited the higher activity and catalytic efficiency for the two substrates compared with GST-PbBGLU1. The transformation of <italic>PbBGLU1</italic> and <italic>PbBGLU16</italic> into <italic>Arabidopsis</italic> identified that the lignin contents of <italic>Arabidopsis BGLU-45</italic> mutant, <italic>PbBGLU1-RE</italic>, and <italic>PbBGLU16-RE</italic> were not changed than that of wild-type. However, compared with wild-type <italic>Arabidopsis</italic>, the overexpression of the plant’s lignin increased in varying degrees. The effect of <italic>PbBGLU16</italic> on the lignin increment was greater than that of <italic>PbBGLU1</italic> in <italic>Arabidopsis</italic>. In pear fruits, with transient overexpression of <italic>PbBGLU1</italic>, the contents of lignin and stone cells were significantly higher (0.01 &lt; <italic>P</italic> &lt; 0.05) than those with empty vector injection pear fruits. After transient expression of <italic>PbBGLU16</italic>, lignin in pear fruit increased significantly (0.01 &lt; <italic>P</italic> &lt; 0.05) and stone cells showed a very significant difference (<italic>P</italic> &lt; 0.01) compared with the control group. However, RNA interference silenced these two genes in pear fruit, which seemed to have no impression on lignin and stone cells. This study provides a molecular biological basis for improving pear fruit quality at the molecular level.</p>