AUTHOR=Gu Linxin , Hou Bing , Chen Xiao , Wang Yu , Chang Pingan , He Xiaohong , Gong Daping , Sun Quan 

TITLE=The Bcl-2-associated athanogene gene family in tobacco (Nicotiana tabacum) and the function of NtBAG5 in leaf senescence

JOURNAL=Frontiers in Plant Science

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2023.1108588

DOI=10.3389/fpls.2023.1108588

ISSN=1664-462X

ABSTRACT=<p>Leaf senescence in tobacco is closely related to leaf maturation and secondary metabolites. Bcl-2-associated athanogene (BAG) family members are highly conserved proteins and play key roles in senescence, growth and development, and resistance to biotic and abiotic stresses. Herein, the BAG family of tobacco was identified and characterized. In total, 19 tobacco BAG protein candidate genes were identified and divided into two classes, class I comprising <italic>NtBAG1a–e</italic>, <italic>NtBAG3a–b</italic>, and <italic>NtBAG4a–c</italic> and class II including <italic>NtBAG5a–e</italic>, <italic>NtBAG6a–b</italic>, and <italic>NtBAG7</italic>. Genes in the same subfamily or branch of the phylogenetic tree exhibited similarities in gene structure and the <italic>cis</italic>-element on promoters. RNA-seq and real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR) revealed that the expression of <italic>NtBAG5c–f</italic> and <italic>NtBAG6a–b</italic> was upregulated in senescent leaves, implying that they play a role in regulating leaf senescence. <italic>NtBAG5c</italic> was localized in the nucleus and cell wall as a homology of leaf senescence related gene <italic>AtBAG5</italic>. Further, the interaction of NtBAG5c with heat-shock protein 70 (HSP70) and sHSP20 was demonstrated using yeast two-hybrid experiment. Virus-induced gene silencing indicated that <italic>NtBAG5c</italic> reduced the lignin content and increased superoxide dismutase (SOD) activity and hydrogen peroxide (H<sub>2</sub>O<sub>2</sub>) accumulation. In <italic>NtBAG5c</italic>-silenced plants, the expression of multiple senescence-related genes cysteine proteinase (<italic>NtCP1)</italic>, <italic>SENESCENCE 4</italic> (<italic>SEN4</italic>) and <italic>SENESCENCE-ASSOCIATED GENE 12</italic> (<italic>SAG12</italic>) was downregulated. In conclusion, tobacco BAG protein candidate genes were identified and characterized for the first time.</p>