AUTHOR=Zhang Jiemei , Yao Zhengping , Zhang Renjun , Mou Zongmin , Yin Honghui , Xu Tianyang , Zhao Dake , Chen Suiyun 

TITLE=Genome-Wide Identification and Expression Profile of the SNAT Gene Family in Tobacco (Nicotiana tabacum)

JOURNAL=Frontiers in Genetics

VOLUME=11

YEAR=2020

URL=https://www.frontiersin.org/journals/genetics/articles/10.3389/fgene.2020.591984

DOI=10.3389/fgene.2020.591984

ISSN=1664-8021

ABSTRACT=<p>Melatonin plays key roles in development and confers stress tolerance to plants. Serotonin <italic>N</italic>-acetyltransferase (SNAT) is either the enzyme involved in the last step or the penultimate enzyme of phytomelatonin biosynthesis. To date, <italic>SNAT</italic> genes have not been characterized in tobacco (<italic>Nicotiana tabacum</italic>), an economically important plant species. The sequence of the Acetyltransf_7 conserved domain was used as a query sequence, and 12 <italic>NtSNAT</italic> candidate genes were in turn identified in the genome of tobacco. These <italic>NtSNAT</italic>s could be divided into two groups based on the phylogenetic tree. <italic>NtSNAT1</italic> and <italic>NtSNAT2</italic> clustered together with the other typical <italic>SNAT</italic>s, but the other 10 <italic>NtSNAT</italic>s separately clustered outside of the typical <italic>SNAT</italic>s. These 10 <italic>NtSNAT</italic>s have only motif 1, whereas representative <italic>SNAT</italic>s, such as <italic>NtSNAT1</italic> and <italic>NtSNAT2</italic> or a <italic>SNAT</italic> from cyanobacteria, have five motifs. In addition, <italic>NtSNAT1</italic> and <italic>NtSNAT2</italic> are highly homologous to the characterized <italic>OsSNAT1</italic>, 62.95 and 71.36%, respectively; however, the homology between the other 10 <italic>NtSNAT</italic> genes and <italic>OsSNAT1</italic> is low. Concomitantly, it is hypothesized that <italic>NtSNAT1</italic> and <italic>NtSNAT2</italic> are the homolog of <italic>SNATs</italic>, whereas the other 10 candidates could be considered <italic>NtSNAT</italic>-like genes. Furthermore, both <italic>Nicotiana tomentosiformis</italic> and <italic>Nicotiana sylvestris</italic>, two diploid ancestor species of <italic>N. tabacum</italic>, have two <italic>SNAT</italic> candidates; therefore, it is speculated that gene rearrangement or deletion during the process of genomic stabilization after whole-genome duplication or polyploidization led to the preservation of <italic>NtSNAT1</italic> and <italic>NtSNAT2</italic> during the evolution of tobacco from the ancestral diploid to the allotetraploid. <italic>NtSNAT</italic> and <italic>NtSNAT</italic>-like genes were differentially expressed in all organs under different stress conditions, indicating that these genes potentially associated with plant growth and development and stress resistance. Under different stress conditions, the expression of <italic>NtSNAT1</italic> was significantly upregulated upon high-temperature and cadmium stresses, while the expression of <italic>NtSNAT2</italic> did not significantly increase under any of the tested stress treatments. These results provide valuable information for elucidating the evolutionary relationship of <italic>SNAT</italic> genes in tobacco and genetic resources for improving tobacco production in the future.</p>