AUTHOR=Jia Peng , Zhang Chenguang , Xing Libo , Li Youmei , Shah Kamran , Zuo Xiya , Zhang Dong , An Na , Han Mingyu , Ren Xiaolin 

TITLE=Genome-Wide Identification of the MdKNOX Gene Family and Characterization of Its Transcriptional Regulation in Malus domestica

JOURNAL=Frontiers in Plant Science

VOLUME=11

YEAR=2020

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2020.00128

DOI=10.3389/fpls.2020.00128

ISSN=1664-462X

ABSTRACT=<p>Knotted1-like Homeobox (KNOX) proteins play important roles in regulating plant growth, development, and other biological processes. However, little information is available on the <italic>KNOX</italic> gene family in apple (<italic>Malus domestica</italic> Borkh.). In this study, 22 <italic>KNOX</italic> genes were identified in the apple genome. The gene structure, protein characteristics, and promoter region were characterized. The <italic>MdKNOX</italic> family members were divided into three classes based on their phylogenetic relationships. Quantitative real-time PCR analysis revealed that the majority of <italic>MdKNOX</italic> genes exhibited strongly preferential expression in buds and were significantly up-regulated during the flower induction period. The transcript levels of <italic>MdKNOX</italic> genes were responsive to treatments with flowering- and stress-related hormones. The putative upstream regulation factor <italic>MdGRF</italic> could directly bind to the promoter of <italic>MdKNOX15</italic> and <italic>MdKNOX19</italic>, and inhibit their transcriptional activities, which were confirmed by yeast one-hybrid and dual-luciferase assays. The results provide an important foundation for future analysis of the regulation and functions of the <italic>MdKNOX</italic> gene family.</p>