NAC Family Transcription Factors in Tobacco and Their Potential Role in Regulating Leaf Senescence.

The NAC family is one of the largest families of plant-specific transcription factors (TFs) and NAC proteins play important regulatory roles in a variety of developmental and stress response processes in plants. Members of the NAC family TFs have been shown to be important regulators of leaf senescence in a number of plant species. Here we report the identification of the NAC family in tobacco ( Nicotiana tabacum ) and characterization of the potential role of some of the tobacco NAC TFs in regulating leaf senescence. A total of 154 NAC genes ( NtNACs ) were identified and clustered together with the Arabidopsis NAC family into fifteen groups (a-o). Transcriptome data analysis followed by qRT-PCR validation showed that the majority of the senescence-up-regulated NtNAC s fall into subgroups NAC-b and f. A number of known senescence regulators from Arabidopsis also belong to these two subgroups. Among these senescence-up-regulated NtNACs , NtNAC080 , a close homolog of AtNAP, is a positive regulator of leaf senescence. Overexpression of NtNAC080 caused early senescence in Arabidopsis leaves and NtNAC080 mutation induced by Cas9/gRNA in tobacco led to delayed leaf senescence.