Genome-wide identification and characterization of aquaporin gene family in moso bamboo (<Emphasis Type="Italic">Phyllostachys edulis</Emphasis>)

Aquaporins (AQPs) are known to play a major role in maintaining water and hydraulic conductivity balance in the plant system. Numerous studies have showed AQPs execute multi-function throughout plant growth and development, including water transport, nitrogen, carbon, and micronutrient acquisition etc. However, little information on AQPs is known in bamboo. In this study, we present the first genome-wide identification and characterization of AQP genes in moso bamboo (Phyllostachys edulis) using bioinformatics. In total, 26 AQP genes were identified by homologous analysis, which were divided into four groups (PIPs, TIPs, NIPs, and SIPs) based on the phylogenetic analysis. All the genes were located on 26 different scaffolds respectively on basis of the gene mapped to bamboo genome. Evolutionary analysis indicated that Ph. edulis was more close to Oryza sativa than Zea mays in the genetic relationship. Besides, qRT-PCR was used to analyze gene expression profiles, which revealed that AQP genes were expressed constitutively in all the detected tissues, and were all responsive to the environmental cues such as drought, water, and NaCl stresses. This data suggested that AQPs may play fundamental roles in maintaining normal growth and development of bamboo, which would contribute to better understanding for the complex regulation mechanism involved in the fast-growing process of bamboo. Furthermore, the result could provide valuable information for further research on bamboo functional genomics.     

Aquaporin gene expression and physiological responses of <Emphasis Type="Italic">Robinia pseudoacacia</Emphasis> L. to the mycorrhizal fungus <Emphasis Type="Italic">Rhizophagus irregularis</Emphasis> and drought stress

The influence of arbuscular mycorrhiza (AM) and drought stress on aquaporin (AQP) gene expression, water status, and photosynthesis was investigated in black locust (Robinia pseudoacacia L.). Seedlings were grown in potted soil inoculated without or with the AM fungus Rhizophagus irregularis, under well-watered and drought stress conditions. Six full-length AQP complementary DNAs (cDNAs) were isolated from Robinia pseudoacacia, named RpTIP1;1, RpTIP1;3, RpTIP2;1, RpPIP1;1, RpPIP1;3, and RpPIP2;1. A phylogenetic analysis of deduced amino acid sequences demonstrated that putative proteins coded by these RpAQP genes belong to the water channel protein family. Expression analysis revealed higher RpPIP expression in roots while RpTIP expression was higher in leaves, except for RpTIP1;3. AM symbiosis regulated host plant AQPs, and the expression of RpAQP genes in mycorrhizal plants depended on soil water condition and plant tissue. Positive effects were observed for plant physiological parameters in AM plants, which had higher dry mass and lower water saturation deficit and electrolyte leakage than non-AM plants. Rhizophagus irregularis inoculation also slightly increased leaf net photosynthetic rate and stomatal conductance under well-watered and drought stress conditions. These findings suggest that AM symbiosis can enhance the drought tolerance in Robinia pseudoacacia plants by regulating the expression of RpAQP genes, and by improving plant biomass, tissue water status, and leaf photosynthesis in host seedlings.     

An aquaporin gene from halophyte <Emphasis Type="Italic">Sesuvium portulacastrum</Emphasis>, <Emphasis Type="Italic">SpAQP1</Emphasis>, increases salt tolerance in transgenic tobacco

Key message

SpAQP1 was strongly induced by salt in an ABA-independent way, promoted seed germination and root growth in transgenic tobaccos and increased salt tolerance by increasing the activities of antioxidative enzymes.

Abstract

Aquaporin (AQP) plays crucial roles in the responses of plant to abiotic stresses such as drought, salt and cold. Compared to glycophytes, halophytes often have excellent salt and drought tolerances. To uncover the molecular mechanism of halophyte Sesuvium portulacastrum tolerance to salt, in this study, an AQP gene, SpAQP1, from S. portulacastrum was isolated and characterized. The amino acid sequence of SpAQP1 shared high homology with that of plant plasma membrane intrinsic proteins (PIPs) and contained the distinct molecular features of PIPs. In the phylogenic tree, SpAQP1 was evidently classified as the PIP2 subfamily. SpAQP1 is expressed in roots, stems and leaves, and was significantly induced by NaCl treatment and inhibited by abscisic acid (ABA) treatment. When heterologously expressed in yeast and tobacco, SpAQP1 enhanced the salt tolerance of yeast strains and tobacco plants and promoted seed germination and root growth under salt stress in transgenic plants. The activity of antioxidative enzymes including superoxide dismutase, peroxidase and catalase was increased in transgenic plants overexpressing SpAQP1. Taken together, our studies suggested that SpAQP1 functioned in the responses of S. portulacastrum to salt stress and could increase salt tolerance by enhancing the antioxidative activity of plants.

     

Investigate of AQP gene expression in the liver of mice after ischemia–reperfusion

Ischemia–reperfusion (IR) injury usually occurs during liver transplantation. Aquaporins (AQPs) are transmembrane channels that facilitate water permeability through cell membranes and are essential for the regulation of water homeostasis. Changes in the AQPs expression have been correlated with several inflammatory diseases. Less is known about AQPs expression in hepatic ischemia reperfusion injury. To clarify the roles of AQPs in IR injury, in this current study we examined the gene expression patterns of AQP1, 8 and 9 in the liver after IR injury. Male balb/c mice were exposed to partial (70%) hepatic ischemia for 65 min and then randomized into five groups of reperfusion [0 h (A), 8 h (B), 1 day (C), 3 days (D), and 7 days (E)]. A surgical group was also selected as the sham group. Serum and liver tissue samples were collected for evaluation of alanine aminotransferase (ALT), aspartate aminotransferase (AST) and liver histopathology. Real time PCR was performed to evaluate the AQPs expression. I/R injury resulted in a significant increase in ALT and AST (p?<?0.05) compared to sham mice in each group. The gene expression of AQPs was significantly increased in the IR group compared with the sham group (p?<?0.05). AQP8 and AQP1 after 8 h (group B) showed the highest gene expression in comparison with other groups, but the highest level of AQP9 gene expression was observed after 1 day (group C). Pathologic changes in the liver after reperfusion were confirmed the IR. In the IR group cytoplasmic vacuolization, inflammatory cell infiltration and focal necrosis were detected. In conclusion, our findings indicated that the damage caused by ischemia–reperfusion in the liver can change the expression of AQP genes, which can interfere with hepatocellular homeostasis and their function. Upregulation of AQP1, 8 and 9 could contribute to the development of hepatocellular swelling after hepatic IR injury.     

Comparative study of the <Emphasis Type="Italic">P2X</Emphasis> gene family in animals and plants

P2X receptors are ligand-gated ion channels that can bind with the adenosine triphosphate (ATP) and have diverse functional roles in neuropathic pain, inflammation, special sense, and so on. In this study, 180 putative P2X genes, including 176 members in 32 animal species and 4 members in 3 species of lower plants, were identified. These genes were divided into 13 groups, including 7 groups in vertebrates and 6 groups in invertebrates and lower plants, through phylogenetic analysis. Their gene organization and motif composition are conserved in most predicted P2X members, while group-specific features were also found. Moreover, synteny relationships of the putative P2X genes in vertebrates are conserved while simultaneously experiencing a series of gene insertion, inversion, and transposition. Recombination signals were detected in almost all of the vertebrates and invertebrates, suggesting that intragenic recombination may play a significant role in the evolution of P2X genes. Selection analysis also identified some positively selected sites that acted on the evolution of most of the predicted P2X proteins. The phenomenon of alternative splicing occurred commonly in the putative P2X genes of vertebrates. This article explored in depth the evolutional relationship among different subtypes of P2X genes in animal and plants and might serve as a solid foundation for deciphering their functions in further studies.     

The obtainment and characteristics of <Emphasis Type="Italic">Kalanchoe pinnata</Emphasis> L. plants expressing the artificial gene of the cecropin P1 antimicrobial peptide

Kalanchoe pinnata L. plants bearing an artificial CP1 gene encoding the cecropin P1 antimicrobial peptide have been obtained. The presence of the CP1 gene in the plant genome has been confirmed by PCR. Cecropin P1 synthesis in transgenic plants has been shown by MALDI mass spectrometry and Western blotting. The obtained plants have been highly resistant to bacterial and fungal phytopathogens, and their extracts have demonstrated antimicrobial activity towards human and animal pathogens. It has been shown that transgenic plants bearing the CP1 gene can be colonized by the beneficial associative microorganisms Methylovorus mays.     

Cloning and functional analysis of two <Emphasis Type="Italic">GmDeg</Emphasis> genes in soybean [<Emphasis Type="Italic">Glycine max</Emphasis> (L.) Merr.]

Although light is the ultimate substrate in photosynthesis, strong light can also be harmful and lead to photoinhibition. The DEG proteases play important roles in the degradation of misfolded and damaged proteins. In this study, two photoinhibition-related genes from soybean [Glycine max (L.) Merr.], GmDeg1 and GmDeg2, were cloned. Bioinformatics analysis indicated that these two proteases both contain a PDZ domain and are serine proteases. The expression levels of GmDeg1 and GmDeg2 increased significantly after 12 h of photooxidation treatment, indicating that GmDeg1 and GmDeg2 might play protective roles under strong light conditions. In in vitro proteolytic degradation assays, recombinant GmDeg1 and GmDeg2 demonstrated biological activities at temperatures ranging from 20°C to 60°C and at pH 5.0 to 8.0. By contrast, the proteases showed no proteolytic effect in the presence of a serine protease inhibitor. Taken together, these results provided strong evidence that GmDeg1 and GmDeg2 are serine proteases that could degrade the model substrate in vitro, indicating that they might degrade damaged D1 protein and other mis-folded proteins in vivo. Furthermore, GmDeg1 and GmDeg2 were transformed into Arabidopsis thaliana to obtain transgenic plants. Leaves from the transgenic and wild-type plants were subjected to strong light conditions in vitro, and the PSII photochemical efficiency (Fv/Fm) was measured. The Fv/Fm of the transgenic plants was significantly higher than that of the wild-type plants at most time points. These results imply that GmDeg1 and GmDeg2 would have similar functions to Arabidopsis AtDeg1, thus accelerating the recovery of PSII photochemical efficiency.     

Water use efficiency in the drought-stressed sorghum and maize in relation to expression of aquaporin genes

Zea mays L. is less tolerant to drought than Sorghum bicolor L. In the present study, we investigated the response of both plants to drought stress applied under field conditions by withholding water for 10 d. The plant growth in terms of shoot fresh and dry masses was more severely reduced in maize than in sorghum, consistently with reduction of leaf relative water content. Gas exchange was also more inhibited by drought in maize than in sorghum. The water use efficiency (WUE) of maize fluctuated during the day and in response to the drought stress. In contrast, sorghum was able to maintain a largely constant WUE during the day in the well-watered plants as well as in the stressed ones. Studying the expression of four aquaporin genes (PIP1;5, PIP1;6, PIP2;3, and TIP1;2) revealed that PIP1;5 in leaves and PIP2;3 in roots were highly responsive to drought in sorghum but not in maize, where they might have supported a greater water transport. The expression pattern of PIP1;6 suggests its possible role in CO₂ transport in control but not droughty leaves of both the plants. TIP1;2 seemed to contribute to water transport in leaves of the control but not droughty plants. We conclude that PIP1;5 and PIP2;3 may have a prominent role in drought tolerance and maintenance of WUE in sorghum plants.     

Assessing the specificity of a herbivore on a plant of uncertain phylogenetic placing: <Emphasis Type="Italic">Listronotus elongatus</Emphasis> a herbivore of <Emphasis Type="Italic">Hydrocotyle ranunculoides</Emphasis>

Hydrocotyle ranunculoides (Araliaceae) is an aquatic plant native to the Americas and invasive in Europe. This work reports laboratory and garden studies on the host range of its main natural enemy, the weevil Listronotus elongatus (Hustache) (Coleoptera: Curculionidae). The genus Hydrocotyle is in a disputed phylogenetic situation such that both Apiaceae and Araliaceae must be included in the test list, but lacking a clear criterion of phylogenetic proximity. For this reason three testing instances were applied: no-choice on excised leaves, no choice on functional plants, and a multiple choice garden experiment. A large initial test-plant list was reduced to a smaller list adjusted by a feeding intensity criterion, survival curves and oviposition levels. Feeding was observed on the excised leaves of 21 out of 36 test plants, but as tests progressed to whole plants L. elongatus showed it could only develop and thrive on its natural host, and possibly survive as adults on Hydrocotyle modesta. Results confirm that typical laboratory starvation tests can provide a dependable ranking of physiological acceptability of different plant species but severely overestimate the actual host range of a specialized herbivore. They also indicate that the phylogenetic criterion for test plant list construction must be approached cautiously if the phylogeny is uncertain or disputed.     

Jasmonic acid modulates xylem development by controlling polar auxin transport in vascular tissues

Development of xylem cells is affected by environmental stresses such as drought and oxidative stress, and recent findings suggested that jasmonic acid (JA) mediates this process through interaction with other phytohormones such as cytokinin. In this study, we showed that polar auxin transport regulated by PIN3 and PIN7 is involved in the JA-mediated xylem development in vascular tissues. The mutant plants that lack the activity of PIN3 and PIN7 responsible for the auxin transport developed extra xylems in vascular tissues such as the JA-treated wild-type plants. Visualization of auxin response and xylem development in the roots treated with NPA, an inhibitor of polar auxin transport, suggested that disruption of polar auxin transport is involved in the xylem phenotype of pin3 pin7 double mutants. We also found that cytokinin increases expressions of PIN3 and PIN7 responsible for the auxin transport while JA decreases only PIN7. These suggested that PIN7-mediated polar auxin transport system modulates xylem development in response to JA. The finding that JA affects auxin distribution in root vascular tissues further supported this. Collectively, these suggest that JA promotes xylem development by disrupting auxin transport in vascular tissues, and the auxin efflux genes, more especially PIN7 whose expression is suppressed by JA mediates this process.