AUTHOR=Fan Sheng , Zhang Dong , Gao Cai , Zhao Ming , Wu Haiqin , Li Youmei , Shen Yawen , Han Mingyu 

TITLE=Identification, Classification, and Expression Analysis of GRAS Gene Family in Malus domestica

JOURNAL=Frontiers in Physiology

VOLUME=8

YEAR=2017

URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2017.00253

DOI=10.3389/fphys.2017.00253

ISSN=1664-042X

ABSTRACT=<p><italic>GRAS</italic> genes encode plant-specific transcription factors that play important roles in plant growth and development. However, little is known about the <italic>GRAS</italic> gene family in apple. In this study, 127 <italic>GRAS</italic> genes were identified in the apple (<italic>Malus domestica</italic> Borkh.) genome and named <italic>MdGRAS1</italic> to <italic>MdGRAS127</italic> according to their chromosomal locations. The chemical characteristics, gene structures and evolutionary relationships of the <italic>MdGRAS</italic> genes were investigated. The 127 <italic>MdGRAS</italic> genes could be grouped into eight subfamilies based on their structural features and phylogenetic relationships. Further analysis of gene structures, segmental and tandem duplication, gene phylogeny and tissue-specific expression with ArrayExpress database indicated their diversification in quantity, structure and function. We further examined the expression pattern of <italic>MdGRAS</italic> genes during apple flower induction with transcriptome sequencing. Eight higher <italic>MdGRAS</italic> (<italic>MdGRAS6, 26, 28, 44, 53, 64, 107</italic>, and <italic>122</italic>) genes were surfaced. Further quantitative reverse transcription PCR indicated that the candidate eight genes showed distinct expression patterns among different tissues (leaves, stems, flowers, buds, and fruits). The transcription levels of eight genes were also investigated with various flowering related treatments (GA<sub>3</sub>, 6-BA, and sucrose) and different flowering varieties (Yanfu No. 6 and Nagafu No. 2). They all were affected by flowering-related circumstance and showed different expression level. Changes in response to these hormone or sugar related treatments indicated their potential involvement during apple flower induction. Taken together, our results provide rich resources for studying <italic>GRAS</italic> genes and their potential clues in genetic improvement of apple flowering, which enriches biological theories of <italic>GRAS</italic> genes in apple and their involvement in flower induction of fruit trees.</p>