Functional characterization of drought-responsive aquaporins in Populus balsamifera and Populus simonii×balsamifera clones with different drought resistance strategies (original) (raw)
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Physiologia Plantarum, 2010
We have characterized poplar aquaporins (AQPs) to investigate their possible functions in differential drought responses of Populus balsamifera and Populus simonii × balsamifera leaves. Plants were exposed to mild and severe levels of drought stress and to drought stress recovery treatment, and their responses were compared with well-watered controls. Compared with P. balsamifera, P. simonii × balsamifera used drought avoidance as the main drought resistance strategy, and rapidly reduced stomatal conductance in response to stress. This strategy is correlated with growth rate reductions. Eleven AQPs were transcriptionally profiled in leaves from these experiments and five were functionally characterized for water channel activity. PIP1;3 and PIP2;5 were among the most highly expressed leaf AQPs that were responsive to drought. Expression of PIP1;3 and five other AQPs increased in response to drought in the leaves of P. simonii × balsamifera but not in P. balsamifera, suggesting a possible role of these AQPs in water redistribution in the leaf tissues. PIP2;5 was upregulated in P. balsamifera, but not in P. simonii × balsamifera, suggesting that this AQP supports the transpiration-driven water flow. Functional characterization of five drought-responsive plasma membrane intrinsic proteins (PIPs) demonstrated that three PIP2 AQPs (PIP2;2, PIP2;5, PIP2;7) functioned as water transporters in Xenopus laevis oocytes, while the two PIP1 AQPs (PIP1;2 and PIP1;3) did not, consistent with the notion that they may be functional only as heterotetramers.
Plant and Cell Physiology, 2008
Plasma membrane intrinsic proteins (PIPs), a type of aquaporins, mediate water transport in many plant species. In this study, we investigated the relationship between the functions of PIP-type water channels and water relations of tobacco plants (Nicotiana tabacum cv. Samsun) under drought stress. Drought stress treatments have led to reductions in the stomatal conductance, transpiration, water potential and turgor pressure in leaves, and also the sap flow rate and osmotic hydraulic conductance in roots. In contrast, leaf osmotic pressure was increased in response to drought stress. Interestingly, the accumulation of NtPIP1;1 and NtPIP2;1 transcripts was significantly decreased, but only that of the NtAQP1 transcript was increased under drought stress. Functional analysis using Xenopus laevis oocytes revealed that NtPIP2;1 shows marked water transport activity, but the activities of NtAQP1 and NtPIP1;1 are weak or almost negligible, respectively, when expressed alone. However, co-expression of NtPIP1;1 with NtPIP2;1 significantly enhanced water transport activity compared with that of NtPIP1;1or NtPIP2;1-expressing oocytes, suggesting that these two aquaporins may function as a water channel, forming a heterotetramer. Heteromerization of NtPIP1;1 and NtPIP2;1 was also suggested by co-expression analyses of NtPIP1;1-GFP (green fluorescent protein) and NtPIP2;1 in Xenopus oocytes. Re-watering treatments recovered water relation parameters and the accumulation of the three NtPIP transcripts to levels similar to control conditions. These results suggest that NtPIP1;1 and NtPIP2;1 play an important role in water transport in roots, and that expression of NtPIP1;1 and NtPIP2;1 is down-regulated in order to reduce osmotic hydraulic conductance in the roots of tobacco plants under drought stress.
Transcriptional regulation of aquaporins in accessions of Arabidopsis in response to drought stress
The Plant Journal, 2010
Aquaporins facilitate water transport over cellular membranes, and are therefore believed to play an important role in water homeostasis. In higher plants aquaporin-like proteins, also called major intrinsic proteins (MIPs), are divided into five subfamilies. We have previously shown that MIP transcription in Arabidopsis thaliana is generally downregulated in leaves upon drought stress, apart from two members of the plasma membrane intrinsic protein (PIP) subfamily, AtPIP1;4 and AtPIP2;5, which are upregulated. In order to assess whether this regulation is general or accession-specific we monitored the gene expression of all PIPs in five Arabidopsis accessions. The overall drought regulation of PIPs was well conserved for all five accessions tested, suggesting a general and fundamental physiological role of this drought response. In addition, significant differences among accessions were identified for transcripts of three PIP genes. Principal component analysis showed that most of the PIP transcriptional variation during drought stress could be explained by one variable linked to leaf water content. Promoter-GUS constructs of AtPIP1;4, AtPIP2;5 and also AtPIP2;6, which is unresponsive to drought stress, had distinct expression patterns concentrated in the base of the leaf petioles and parts of the flowers. The presence of drought stress response elements within the 1.6-kb promoter regions of AtPIP1;4 and AtPIP2;5 was demonstrated by comparing transcription of the promoter reporter construct and the endogenous gene upon drought stress. Analysis by ATTED-II and other web-based bioinformatical tools showed that several of the MIPs downregulated upon drought are strongly co-expressed, whereas AtPIP1;4, AtPIP2;5 and AtPIP2;6 are not co-expressed.
Whole Gene Family Expression and Drought Stress Regulation of Aquaporins
Plant Molecular Biology, 2005
Since many aquaporins (AQPs) act as water channels, they are thought to play an important role in plant water relations. It is therefore of interest to study the expression patterns of AQP isoforms in order to further elucidate their involvement in plant water transport. We have monitored the expression patterns of all 35 Arabidopsis AQPs in leaves, roots and flowers by cDNA microarrays, specially designed for AQPs, and by quantitative real-time reverse transcriptase PCR (Q-RT-PCR). This showed that many AQPs are pre-dominantly expressed in either root or flower organs, whereas no AQP isoform seem to be leaf specific. Looking at the AQP subfamilies, most plasma membrane intrinsic proteins (PIPs) and some tonoplast intrinsic proteins (TIPs) have a high level of expression, while NOD26-like proteins (NIPs) are present at a much lower level. In addition, we show that PIP transcripts are generally down-regulated upon gradual drought stress in leaves, with the exception of AtPIP1;4 and AtPIP2;5, which are upregulated. AtPIP2;6 and AtSIP1;1 are constitutively expressed and not significantly affected by the drought stress. The transcriptional down-regulation of PIP genes upon drought stress could also be observed on the protein level.
Aquaporins as potential drought tolerance inducing proteins: Toward instigating stress tolerance
Journal of Proteomics, 2017
Aquaporins (AQPs) are primarily involved in maintaining cellular water homeostasis. Their role in diverse physiological processes has fascinated plant scientists for more than a decade, particularly concerning abiotic stresses. Increasing examples of evidence in various crop plants indicate that the AQPs are responsible for precise regulation of water movement and consequently play a crucial role in the drought stress tolerance. Since drought is one of the major abiotic stresses affecting agricultural production worldwide, it has become a critical agenda to focus research on the development of drought tolerant crop plants. AQPs can act as key candidate molecules to confront this issue. Hence there is an important need to explore the potential of AQPs by understanding the molecular mechanisms and pathways through which they induce drought tolerance. Moreover, the signalling network/s involved in such pathways needs to be mined and understood correctly, and that may lead to the development of drought tolerance in crop plants. In the present review, opportunity and challenges regarding the efficient utilization of AQP-related information is presented and discussed. The complied information and the discussion will be helpful for designing future experiments and to set the specific goals for the enhancement of drought tolerance in crop plants.
Aquaporins as potential drought tolerance inducing proteins: Towards instigating stress tolerance
Journal of Proteomics, 2017
Aquaporins (AQPs) are primarily involved in maintaining cellular water homeostasis. Their role in diverse physiological processes has fascinated plant scientists for more than a decade, particularly concerning abiotic stresses. Increasing examples of evidence in various crop plants indicate that the AQPs are responsible for precise regulation of water movement and consequently play a crucial role in the drought stress tolerance. Since drought is one of the major abiotic stresses affecting agricultural production worldwide, it has become a critical agenda to focus research on the development of drought tolerant crop plants. AQPs can act as key candidate molecules to confront this issue. Hence there is an important need to explore the potential of AQPs by understanding the molecular mechanisms and pathways through which they induce drought tolerance. Moreover, the signalling network/s involved in such pathways needs to be mined and understood correctly, and that may lead to the development of drought tolerance in crop plants. In the present review, opportunity and challenges regarding the efficient utilization of AQP-related information is presented and discussed. The complied information and the discussion will be helpful for designing future experiments and to set the specific goals for the enhancement of drought tolerance in crop plants.
Gene, 2011
Water uptake across cell membranes is a principal requirement for plant growth at both the cellular and whole-plant levels; water movement through plant membranes is regulated by aquaporins (AQPs) or major intrinsic proteins (MIPs). We examined the expression characteristics of the poplar plasma membrane intrinsic protein 1 gene (PatPIP1), a type of MIP, which was isolated from a suspension cell cDNA library of Populus alba × P. tremula var. glandulosa. Examination of protoplasts expressing the p35S-PatPIP1::sGFP fusion protein revealed that the protein was localized in the plasma membrane. Northern blot analysis revealed that the gene was strongly expressed in poplar roots and leaves. Gene expression was inducible by abiotic factors including drought, salinity, cold temperatures and wounding, and also by plant hormones including gibberellic acid, jasmonic acid and salicylic acid. Since we found that the PatPIP1 gene was strongly expressed in response to mannitol, NaCl, jasmonic acid and wounding, we propose that PatPIP1 plays an essential role in the defense of plants against water stress.
The role of aquaporins in cellular and whole plant water balance
Biochimica et Biophysica Acta (BBA) - Biomembranes, 2000
Aquaporins are water channel proteins belonging to the major intrinsic protein (MIP) superfamily of membrane proteins. More than 150 MIPs have been identified in organisms ranging from bacteria to animals and plants. In plants, aquaporins are present in the plasma membrane and in the vacuolar membrane where they are abundant constituents. Functional studies of aquaporins have hitherto mainly been performed by heterologous expression in Xenopus oocytes. A main issue is now to understand their role in the plant, where they are likely to be important both at the cellular and at the whole plant level. Plants contain a large number of aquaporin isoforms with distinct cell type-and tissue-specific expression patterns. Some of these are constitutively expressed, whereas the expression of others is regulated in response to environmental factors, such as drought and salinity. At the protein level, regulation of water transport activity by phosphorylation has been reported for some aquaporins. ß Major intrinsic protein; Plasma membrane intrinsic protein; Tonoplast intrinsic protein 0005-2736 / 00 / $^see front matter ß 2000 Elsevier Science B.V. All rights reserved. PII: S 0 0 0 5 -2 7 3 6 ( 0 0 ) 0 0 1 4 7 -4 * Corresponding
Date-Palm Aquaporins PdPIP1; 1 and PdPIP1; 3 Are Involved in Early Drought Stress Response
Aquaporins - water channels, play fundamental roles in regulating the osmotic water permeability of plant cells. This study characterizes the aquaporin genes of date-palm - a dessert oasis monocot tree. Thirty three aquaporin genes were detected by bioinformatic analysis of the date-palm genome. Full-length cDNA clones encoding aquaporins were isolated from date-palm seedlings. A differential expression of aquaporins genes was identified in various tissues under normal and abiotic stress. The genes of the plasma membrane intrinsic protein (PIP genes), PdPIP1;1, and PdPIP1;3, code for 287 amino acids, having 96% homology to PIP 1;1 genes of Elaeis guineensis and Oryza sativa. A peak in the expression level of PdPIP1; 1 and PdPIP1; 3, was detected at early stages of drought stress in the roots, while very low expression level without a significant change was observed in the leaves. It is suggested that these two PIP genes play a role in the date-palm early response to drought. Transient expression of PdPIP1;1 in Arabidopsis protoplasts resulted in increased osmotic water permeability, indicating the in-vivo function of this protein as a water channel.
Annals of Botany, 2006
Background and Aims Drought causes a decline of root hydraulic conductance, which aside from embolisms, is governed ultimately by aquaporins. Multiple factors probably regulate aquaporin expression, abundance and activity in leaf and root tissues during drought; among these are the leaf transpiration rate, leaf water status, abscisic acid (ABA) and soil water content. Here a study is made of how these factors could influence the response of aquaporin to drought. Methods Three plasma membrane intrinsic proteins (PIPs) or aquaporins were cloned from Phaseolus vulgaris plants and their expression was analysed after 4 d of water deprivation and also 1 d after re-watering. The effects of ABA and of methotrexate (MTX), an inhibitor of stomatal opening, on gene expression and protein abundance were also analysed. Protein abundance was examined using antibodies against PIP1 and PIP2 aquaporins. At the same time, root hydraulic conductance (L), transpiration rate, leaf water status and ABA tissue concentration were measured. Key Results None of the treatments (drought, ABA or MTX) changed the leaf water status or tissue ABA concentration. The three treatments caused a decline in the transpiration rate and raised PVPIP2;1 gene expression and PIP1 protein abundance in the leaves. In the roots, only the drought treatment raised the expression of the three PIP genes examined, while at the same time diminishing PIP2 protein abundance and L. On the other hand, ABA raised both root PIP1 protein abundance and L. Conclusions The rise of PvPIP2;1 gene expression and PIP1 protein abundance in the leaves of P. vulgaris plants subjected to drought was correlated with a decline in the transpiration rate. At the same time, the increase in the expression of the three PIP genes examined caused by drought and the decline of PIP2 protein abundance in the root tissues were not correlated with any of the parameters measured.