Identification of the Tonoplast Intrinsic Aquaporin Genes in Eucalyptus grandis and Characterization of EgTIP2, an Osmotic Stress-Responsive Gene

Aquaporins are implicated in various physiological processes in plants, including growth, development and adaptation to stress. In this context, aquaporins are reported to play relevant roles in plant tolerance to unfavorable drought conditions. In this study, we have focused on the molecular characterization of a root-specific TIP gene (tonoplast intrinsic aquaporin named EgTIP2.2) from Eucalyptus grandis and investigated the composition of the TIP subfamily in this species. For this, searches in the Phytozome database using known Populus TIP coding genes as queries were performed. These searches revealed the presence of nine putative TIP genes in the eucalyptus genome, which could be individually assigned by phylogeny to the classical TIP1–5 groups. The distribution of the target transcripts in different E. grandis organs/tissues, as determined by RT-qPCR and RNA-Seq analyses, indicated expression mainly in root and stem, highlighting the root- and stem-restricted expression of EgTIP2.2 and EgTIP4.1, respectively. The responsiveness of the root-specific EgTIP2.2 gene to dehydration was further evaluated in roots of eucalyptus seedlings treated with polyethylene glycol (PEG). As a result, EgTIP2.2 expression was shown to be induced after 6 and 24 h of seedling exposure to PEG-8000. Additional in silico analysis using the ScyllaEST database pointed to an involvement of the identified TIP genes in abiotic stress responses. Overall, the obtained results suggest that these novel EgTIPs are functionally implicated in eucalyptus adaptation to stress.

Keywords: aquaporin; tissue-specificity; abiotic stress; phylogeny.

Support: Cnpq and Fapesp