In order to compare the salt-transcriptional response of ‘Porto’ and ‘Sunny wind’ cultivars on flower growth, a floral tissue-specific microarray analysis was performed treating the plants with 100 mM of NaCl since at this concentration for both cultivars all of the plants still continue to flowering (to produce flowers). Gene transcripts that are present in floral tissue of a particular cultivar and gene transcripts that are present in higher abundance in these tissues are valuable for understanding the biological and metabolic processes during salinity tolerance mechanisms. In general, different transcriptional profiles were obtained in the more tolerant ‘Porto’ cultivar and the moderately sensitive ‘Sunny wind’ under salt-stressed and unstressed conditions. In response to salt stress, the differential regulation of a relatively larger number of floral specific genes between the cultivars was observed and these findings suggested that the degree of salt tolerance may be directly linked to the extent of transcriptome modification by salt stress. Among the common responses between the different floral tissues in ‘Porto’ and ‘Sunny wind’ cultivars, an interesting downregulated gene in petals and SO was the DREB that has been associated with salinity tolerance in different plant species. Functional studies in Arabidopsis demonstrated that overexpression of
GhDREB1 increased sensitivity to high salinity (Dong et al.
2010). DREB gene has been supposed to act as transcriptional repressor for DRE-mediated gene expression (Huang and Liu
2006). However, in tomato plants exposed to salinity the expression of SlDREB2 and SlDRB3 showed an increase during the first 12 h and then the trend declined (Islam and Wang
2009; Hichri et al.
2016). These findings remark the importance of DREB, but their function could be associated with early adaptation responses to salinity. Among the upregulated genes there were coat protein (COP) genes that seems to be associated to salt tolerance. Functional analysis using mutants with loss function of COP genes showed higher sensitivity to salinity, demonstrating the importance of these genes under salt stress (Sánchez-Simarro et al.
2020). Another highly expressed gene was the alcohol dehydrogenase (ADH) gene which has been found expressed in both cultivars but with different abundance. In detail, in this study, five ADH genes commonly regulated in petals of both cultivar and eight only in ‘Porto’ were identified. The incorporation of ADH genes from
Synechocystis sp. PCC 690 in tobacco plants resulted in transgenic
N. benthamiana plants with enhanced salt tolerance (Yi et al.
2017). Moreover, transgenic lines grown under 300 mM NaCl also showed higher expression level of stress-related genes such as
DREB2A, responsive to desiccation 29 (RD29), and HSP17.6 (Yi et al.
2017). The higher number of ADH transcripts found in ‘Porto’ floral tissues may be involved in defence responses when challenged by abiotic stress for a stress-induced signal transduction leading to the activation of salt-tolerance-related responses.