Investigation and Characterization of Eucalyptus Tonoplast Intrinsic Protein (EgTIP) Gene Subfamily

Plant aquaporins are water channels implicated in various physiological processes, including growth, development and adaptation to stress. In this study, the Tonoplast Intrinsic Protein (TIP) gene subfamily of Eucalyptus, an important woody species, was investigated and characterized. A genome-wide survey of the eucalyptus genome revealed the presence of ten putative TIP genes, which were individually assigned by phylogeny to each of the classical TIP1–5 groups. Homology modelling confirmed the presence of the two highly conserved Asn-Pro-Ala (NPA) motifs in the identified E. grandis TIPs (EgTIP) and revealed variations in the selectivity filter that might be implicated in their substrate selectivity. The distribution of the target transcripts in different E. grandis organs/tissues revealed distinct expression patterns, including a set of organ/tissue-enriched genes. Additional gene expression profiling using a Eucalyptus EST database pointed to an involvement of the identified genes in abiotic stress responses. The presence in the 5´-upsteam regions of the identified EgTIP genes of common cis-regulatory elements involved in abiotic stress and hormone responses corroborates this idea. Overall, the obtained results suggest that these novel EgTIPs are functionally implicated in eucalyptus adaptation to stress.

Keyword: aquaporin, expression, genomic organization, protein structure

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