AUTHOR=Meng Jia-Xin , Wei Jun , Chi Ru-Fei , Qiao Yu-Hang , Zhou Jing , Wang Yi-Lin , Wang Han , Li Hou-Hua 

TITLE=MrMYB44-Like Negatively Regulates Anthocyanin Biosynthesis and Causes Spring Leaf Color of Malus ‘Radiant’ to Fade From Red to Green

JOURNAL=Frontiers in Plant Science

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2022.822340

DOI=10.3389/fpls.2022.822340

ISSN=1664-462X

ABSTRACT=<p>The “Spring-red-leaf” crabapple cultivar has young red leaves and mature green leaves. However, the mechanism of anthocyanin biosynthesis in crabapple leaves in spring remains unknown. In this study, Illumina RNA sequencing (RNA-Seq) was performed on <italic>Malus</italic> ‘Radiant’ leaf tissues in different stages of development. Twenty-two genes in the anthocyanin biosynthesis pathway and 44 MYB transcription factors (TFs) were significantly enriched among differentially expressed genes (DEGs). Three R2R3-MYB TFs in subgroup 22 of the MYB TF family, <italic>MrMYB44-like1</italic>, <italic>MrMYB44-like2</italic>, and <italic>MrMYB44-like3</italic>, were highly expressed in green leaves according to RNA-Seq and quantitative real-time quantitative PCR results. Their expression levels were negatively correlated with anthocyanin content. In transient assays, overexpression of <italic>MrMYB44-like1</italic>, <italic>MrMYB44-like2</italic>, or <italic>MrMYB44-like3</italic> inhibited anthocyanin accumulation and reduced pigment in leaf disks of <italic>M</italic>. ‘Radiant’ and fruit peels of <italic>M. domestica</italic> ‘Fuji.’ When the conserved region of the three <italic>MrMYB44-like</italic>s was silenced, the anthocyanin biosynthesis pathway was activated and pigments increased in both tissues. Moreover, bimolecular fluorescence complementation assays showed <italic>MrMYB44-like</italic>s interacted with <italic>MrWRKY6</italic> to form protein complexes that regulated anthocyanin biosynthesis.</p>