The Eucalyptus Tonoplast Intrinsic Protein (TIP) Gene Subfamily: Genomic Organization, Structural Features, and Expression Profiles

Abstract

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 economically important woody species, was investigated and characterized. A genome-wide survey of the Eucalyptus grandis genome revealed the presence of eleven putative TIP genes (referred as EgTIP), which were individually assigned by phylogeny to each of the classical TIP1–5 groups. Homology modeling confirmed the presence of the two highly conserved NPA (Asn-Pro-Ala) motifs in the identified EgTIPs. Residue variations in the corresponding selectivity filters, that might reflect differences in EgTIP substrate specificity, were observed. All EgTIP genes, except EgTIP5.1, were transcribed and the majority of them showed organ/tissue-enriched expression. Inspection of the EgTIP promoters revealed the presence of common cis-regulatory elements implicated in abiotic stress and hormone responses pointing to an involvement of the identified genes in abiotic stress responses. In line with these observations, additional gene expression profiling demonstrated increased expression under polyethylene glycol-imposed osmotic stress. Overall, the results obtained suggest that these novel EgTIPs might be functionally implicated in eucalyptus adaptation to stress.

Genome-Wide Identification, Structure Characterization, and Expression Pattern Profiling of the Aquaporin Gene Family in Betula pendula

“…This last group is relatively rare in most plant species [ 86 ]; and our results confirmed the variability of the TIPs observed in plants. The diversity observed in the ar/R selectivity filter in the different Bpe TIP subgroups is similar to the TIPs from other plant species [ 5 , 6 , 7 , 13 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 ]. The FPs are well conserved between members, mainly composed of (T, S, A, Y, W), except for Bpe TIP5;1 with (V, A, A, Y, W) residues.…”

“…This lower average p I value of the Bpe TIPs (average 5.72), compared with the four other subfamilies ( p I > 6.5, except for Bpe PIP2;2-3, Bpe XIP1s and Bpe NIP5;1 which have p I < 6.5), is linked to the absence of the basic residues in the C -terminal domains of the proteins. This relationship was previously described in Arabidopsis [ 2 ], eucalyptus [ 45 ] and olive [ 5 ]. The p I could reflect a functional constraint imposed on the MIPs, including the specific key regulation sites across the C -terminal regions involved in phosphorylation, methylation, sorting signals, and the interaction with regulating partners, which differ between MIP families.…”

“…The increasing number of sequenced plant genomes opens new horizons in the study of functional genomics and the precision of annotating new subfamily genes, manipulating them to potentially enhance plant performance and resilience to ever-changing environmental conditions. In this regard, AQP diversity has been studied in different ligneous species, including Camellia sinensis [ 42 ], Citrus sinensis [ 43 ], Coffea canephora [ 44 ], Eucalyptus grandis and E. globulus [ 45 , 46 ], Gossypium hirsutum [ 7 , 47 ], Hevea brasiliensis [ 48 ], Jatropha curcas [ 49 ], Malus domestica [ 50 ], Olea europaea [ 5 ], Populus trichocarpa [ 6 , 13 ], and Vitis vinifera [ 51 ]. Irrespective of whether AQP studies are carried out on perennial or annual species, they all demonstrate how AQPs support significant roles in the cellular homeostasis of different organs and tissues and in the radial and systemic transport of permeants, by increasing the permeability of various membranes to water and essential nutrients in response to any fluctuating demands (nutrition, transpiration, etc.)…”

Drought stress and re-watering affect the abundance of TIP aquaporin transcripts in barley

“…The organ- and development-specificity of the TIP5;1 and TIP3;2 isoforms has also been proven in other species. The Arabidopsis AtTIP5;1 gene was found to be expressed only in the sperm cell, stamen and pollen [33], while in Eucalyptus species, EgTIP5;1 was the only gene from the TIP subfamily that appeared to be nonfunctional [34]. Another TIP isoform, TIP3;2 , which was not expressed in the barley leaves in our study, had been highly specifically expressed in A .…”

Genome-wide identification of multifunctional laccase gene family in Eucalyptus grandis: potential targets for lignin engineering and stress tolerance

“…To investigate the oxidative and osmotic stress-inducible expression patterns of a set of selected Eucalyptus laccases genes, stress imposition was performed essentially as described (Rodrigues et al 2016). Briefly, 4-month-old plantlets (n = 15) grown in Hoagland's nutrient solution 75% were treated with 100 mM H 2 O 2 (for oxidative stress induction) or PEG8000 (for osmotic stress induction; osmotic potential of − 0.8 MPa) for 6, 12 and 24 h. Plantlets (n = 15) maintained in Hoagland's solution 75% were used as control.…”