Olea europaea L. is a typical Mediterranean tree of great economic and agronomic importance which is adapted to arid climates. The molecular bases of water transport in olive trees have not been studied up to now, and there is no olive aquaporin-like nucleotidic sequences in the databases. Aquaporins (MIPs) belong to a family of channel proteins that facilitate water and neutral solutes transport across the membrane and down a water potential gradient. Deduced amino acid sequences encoded by cDNAa related to the MIP gene family from Olea europaea were characterized. A phylogenetic analysis of the products of corresponding genes named OePIP1, OePIP2 and OeTIP confirmed that they are water channel proteins localized in the plasma membrane and in the tonoplast. The sequences were obtained by rapid amplification of cDNA ends (RACE-PCR). The DNA OePIP1 consists of 1275 bp, while OePIP2 and OeTIP of 1403 bp and 1123 bp respectively. The biological activity of OePIPs was proved using the Xenopus laevis oocyte-swelling assay. The expression of these aquaporin genes in shoot under drought stress in olive was analyzed in parallel with the assessment of shoot hydraulic conductivity and incidence of embolization in the shoot. To investigate the effect of drought on shoot water transport and the transcript level of OeMIPs genes in shoot, the olive trees were subjected to drought treatment (the irrigation was suspended for a period of 3 weeks) and the expression levels of the aquaporins were measured by Northern analysis. The results indicated that the transcript levels of each OeMIPs diminished strongly in droughtstressed plants compared to non stressed control plants. Lower aquaporin expression coupled with a reduction in shoot hydraulic conductivity and with an increasing extent of xylem vessel embolisation. The down regulation of these genes, resulting in reduced membrane water permeability, reduced water transport in the shoot, to probably promote cellular water conservation during a period of dehydration. A possible role to modulate shoot embolisation during drought was proposed for aquaporins.
Hydraulic conductivity and expression of aquaporin genes in in Olea europaea L. shoots under drought stress
LOVISOLO, Claudio;SECCHI, Francesca;SCHUBERT, Andrea
2005-01-01
Abstract
Olea europaea L. is a typical Mediterranean tree of great economic and agronomic importance which is adapted to arid climates. The molecular bases of water transport in olive trees have not been studied up to now, and there is no olive aquaporin-like nucleotidic sequences in the databases. Aquaporins (MIPs) belong to a family of channel proteins that facilitate water and neutral solutes transport across the membrane and down a water potential gradient. Deduced amino acid sequences encoded by cDNAa related to the MIP gene family from Olea europaea were characterized. A phylogenetic analysis of the products of corresponding genes named OePIP1, OePIP2 and OeTIP confirmed that they are water channel proteins localized in the plasma membrane and in the tonoplast. The sequences were obtained by rapid amplification of cDNA ends (RACE-PCR). The DNA OePIP1 consists of 1275 bp, while OePIP2 and OeTIP of 1403 bp and 1123 bp respectively. The biological activity of OePIPs was proved using the Xenopus laevis oocyte-swelling assay. The expression of these aquaporin genes in shoot under drought stress in olive was analyzed in parallel with the assessment of shoot hydraulic conductivity and incidence of embolization in the shoot. To investigate the effect of drought on shoot water transport and the transcript level of OeMIPs genes in shoot, the olive trees were subjected to drought treatment (the irrigation was suspended for a period of 3 weeks) and the expression levels of the aquaporins were measured by Northern analysis. The results indicated that the transcript levels of each OeMIPs diminished strongly in droughtstressed plants compared to non stressed control plants. Lower aquaporin expression coupled with a reduction in shoot hydraulic conductivity and with an increasing extent of xylem vessel embolisation. The down regulation of these genes, resulting in reduced membrane water permeability, reduced water transport in the shoot, to probably promote cellular water conservation during a period of dehydration. A possible role to modulate shoot embolisation during drought was proposed for aquaporins.
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