AUTHOR=Xiong Wangdan , Li Yu , Wu Zhenying , Ma Lichao , Liu Yuchen , Qin Li , Liu Jisheng , Hu Zhubing , Guo Siyi , Sun Juan , Yang Guofeng , Chai Maofeng , Zhang Chunyi , Lu Xiaoduo , Fu Chunxiang 

TITLE=Characterization of Two New brown midrib1 Mutations From an EMS-Mutagenic Maize Population for Lignocellulosic Biomass Utilization

JOURNAL=Frontiers in Plant Science

VOLUME=11

YEAR=2020

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2020.594798

DOI=10.3389/fpls.2020.594798

ISSN=1664-462X

ABSTRACT=<p>Gene mutations linked to lignin biosynthesis are responsible for the <italic>brown midrib (bm)</italic> phenotypes. The <italic>bm</italic> mutants have a brown-reddish midrib associated with changes in lignin content and composition. Maize <italic>bm1</italic> is caused by a mutation of the cinnamyl alcohol dehydrogenase gene <italic>ZmCAD2</italic>. Here, we generated two new <italic>bm1</italic> mutant alleles (<italic>bm1-E1</italic> and <italic>bm1-E2</italic>) through EMS mutagenesis, which contained a single nucleotide mutation (Zm<italic>cad2-1</italic> and Zm<italic>cad2-2</italic>). The corresponding proteins, ZmCAD2-1 and ZmCAD2-2 were modified with Cys103Ser and Gly185Asp, which resulted in no enzymatic activity <italic>in vitro</italic>. Sequence alignment showed that CAD proteins have high similarity across plants and that Cys103 and Gly185 are conserved in higher plants. The lack of enzymatic activity when Cys103 was replaced for other amino acids indicates that Cys103 is required for its enzyme activity. Enzymatic activity of proteins encoded by <italic>CAD</italic> genes in <italic>bm1-E</italic> plants is 23–98% lower than in the wild type, which leads to lower lignin content and different lignin composition. The <italic>bm1-E</italic> mutants have higher saccharification efficiency in maize and could therefore provide new and promising breeding resources in the future.</p>