AUTHOR=Chai Wenbo , Peng Xiaojian , Liu Bin , Wang Jing , Zhu Zhan , Liu Yin , Zhao Kai , Cheng Beijiu , Si Weina , Jiang Haiyang 

TITLE=Comparative Genomics, Whole-Genome Re-sequencing and Expression Profile Analysis of Nucleobase:Cation Symporter 2 (NCS2) Genes in Maize

JOURNAL=Frontiers in Plant Science

VOLUME=9

YEAR=2018

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2018.00856

DOI=10.3389/fpls.2018.00856

ISSN=1664-462X

ABSTRACT=<p>Nucleobase:cation symporter 2 (NCS2) proteins are important for the transport of free nucleobases, participating in diverse plant growth and developmental processes, as well as response to abiotic stress. To date, a comprehensive analysis of the <italic>NCS2</italic> gene family has not been performed in maize. In this study, we conducted a comparative genomics analysis of <italic>NCS2</italic> genes in 28 plant species, ranging from aquatic algae to land plants, concentrating mainly on maize. Gene duplication events contributed to the expansion of <italic>NCS2</italic> genes from lower aquatic plants to higher angiosperms, and whole-genome/segmental and single-gene duplication events were responsible for the expansion of the maize <italic>NCS2</italic> gene family. Phylogenetic construction showed three <italic>NCS2</italic> subfamilies, I, II, and III. According to homology-based relationships, members of subfamily I are <italic>NCS2/AzgA-like</italic> genes, whereas those in subfamilies II and III are <italic>NCS2/NAT</italic>s. Moreover, subfamily I exhibited ancient origins. A motif compositional analysis showed that one symbolic motif (motif 4) of the <italic>NCS2/NAT</italic> genes was absent in subfamily I. In maize, three <italic>NCS2/AzgA-like</italic> and 21 <italic>NCS2/NAT</italic> genes were identified, and purifying selection influenced the duplication of maize <italic>NCS2</italic> genes. Additionally, a population genetic analysis of <italic>NCS2</italic> genes revealed that <italic>ZmNCS2–21</italic> showed the greatest diversity between the 78 inbred and 22 wild surveyed maize populations. An expression profile analysis using transcriptome data and quantitative real-time PCR revealed that <italic>NCS2</italic> genes in maize are involved in diverse developmental processes and responses to abiotic stresses, including abscisic acid, salt (NaCl), polyethylene glycol, and low (4°C) and high (42°C) temperatures. <italic>ZmNCS2</italic> genes with relatively close relationships had similar expression patterns, strongly indicating functional redundancy. Finally, <italic>ZmNCS2–16</italic> and <italic>ZmNCS2–23</italic> localize in the plasma membrane, which confirmed their predicted membrane structures. These results provide a foundation for future studies regarding the functions of ZmNCS2 proteins, particularly those with potentially important roles in plant responses to abiotic stresses.</p>