AUTHOR=Zheng Jie , Liu Longbo , Tao Huihui , An Yuyan , Wang Liangju 

TITLE=Transcriptomic Profiling of Apple Calli With a Focus on the Key Genes for ALA-Induced Anthocyanin Accumulation

JOURNAL=Frontiers in Plant Science

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2021.640606

DOI=10.3389/fpls.2021.640606

ISSN=1664-462X

ABSTRACT=<p>The red color is an attractive trait of fruit and determines its market acceptance. 5-Aminolevulinic acid (ALA), an eco-friendly plant growth regulator, has played a universal role in plant secondary metabolism regulation, particularly in flavonoid biosynthesis. It has been widely reported that ALA can up-regulate expression levels of several structural genes related to flavonoid metabolism and anthocyanin accumulation. However, the molecular mechanisms behind ALA-induced expression of these genes are complicated and still far from being completely understood. In this study, transcriptome analysis identified the differentially expressed genes (DEGs) associated with ALA-induced anthocyanin accumulation. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that the flavonoid biosynthesis (ko00941) pathway was significantly enhanced in the ALA-treated apple calli at 24, 48, and 72 h after the treatment. Expression pattern revealed that ALA up-regulated the expression of the structural genes related to not only anthocyanin biosynthesis (<italic>MdCHS</italic>, <italic>MdCHI</italic>, <italic>MdF3’H</italic>, <italic>MdDFR</italic>, <italic>MdANS</italic>, and <italic>MdUFGT</italic>) but also anthocyanin transport (<italic>MdGST</italic> and <italic>MdMATE</italic>). Two R2R3-MYB transcription factors (MdMYB10 and MdMYB9), which are the known positive regulators of anthocyanin biosynthesis, were significantly induced by ALA. Gene overexpression and RNA interference assays demonstrated that <italic>MdMYB10</italic> and <italic>MdMYB9</italic> were involved in ALA-induced anthocyanin biosynthesis. Moreover, MdMYB10 and MdMYB9 might positively regulate the transcription of <italic>MdMATE8</italic> by binding to the promoter region. These results indicate that <italic>MdMYB10</italic> and <italic>MdMYB9</italic> modulated structural gene expression of anthocyanin biosynthesis and transport in response to ALA-mediated apple calli coloration at the transcript level. We herein provide new details regarding transcriptional regulation of ALA-induced color development.</p>