Genome-Wide Identification and Expression Analysis of the Phytocyanin Gene Family in Nicotiana tabacum

Phytocyanin (PC) is a class of plant-specific blue copper proteins involved in electron transport, plant growth, development, and stress resistance. However, PC proteins have not been systematically evaluated in tobacco plants. We determined the whole-genome sequences of the PC family in the tobacco cultivar 'K326.' The transcriptome data were used to analyze the expression of the NtPC family at different development stages and tissue-specific genes. Real-time fluorescence quantitative analysis was used to analyze the expression of the NtPC gene family under low temperature and methyl jasmonate stress. The tobacco NtPC family contained 110 members and was divided into four subfamilies: early nodulin-like protein (NtENODL), uclacyanin-like protein, stellacyanin1-like protein, and plantacyanin-like protein. According to phylogenetic and structural analyses, the NtPC family could be divided into eight structural types. Fifty-three NtPCs were randomly distributed on 22 of 24 tobacco chromosomes. Collinearity analysis revealed 33 pairs of genes belonging to the NtPC family. Gene ontology analysis showed that the PC genes are components of the plasma membrane and may participate in plasma membrane-related functions. The NtPC family contained numerous elements related to hormonal and abiotic stress responses and was specifically expressed in the tobacco prosperous, maturation, and budding periods. Tissue-specific expression analysis showed that some genes were tissue specific. The expression of NtENODL58 and other genes was significantly induced by low-temperature and methyl jasmonate stress. Thus, the NtPC gene family plays an important role in plant stress response.