The varied functions of aluminium-activated malate transporters–much more than aluminium resistance

The ALMT (aluminium-activated malate transporter) family comprises a functionally diverse but structurally similar group of ion channels. They are found ubiquitously in plant species, expressed throughout different tissues, and located in either the plasma membrane or tonoplast. The first family member identified was TaALMT1, discovered in wheat root tips, which was found to be involved in aluminium resistance by means of malate exudation into the soil. However, since this discovery other family members have been shown to have many other functions such as roles in stomatal opening, general anionic homoeostasis, and in economically valuable traits such as fruit flavour. Recent evidence has also shown that ALMT proteins can act as key molecular actors in GABA (γ-aminobutyric acid) signalling, the first evidence that GABA can act as a signal transducer in plants.

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Split personality of Aluminum Activated Malate Transporter family proteins: facilitation of both GABA and malate transport

10.1101/215335 ◽

2017 ◽

Cited By ~ 1

Author(s):

Sunita A. Ramesh ◽

Muhammad Kamran ◽

Wendy Sullivan ◽

Larissa Chirkova ◽

Mamoru Okamoto ◽

...

Keyword(s):

Wheat Root ◽

Gaba Uptake ◽

Gamma Aminobutyric Acid ◽

In Planta ◽

Root Tips ◽

Anion Transporters ◽

Transporter Family ◽

Malate Transport ◽

Split Personality ◽

Heterologous Expression Systems

ABSTRACTPlant aluminum activated malate transporters (ALMTs) are currently classified as anion channels; they are also known to be regulated by diverse signals leading to a range of physiological responses. Gamma-aminobutyric acid (GABA) regulation of anion flux through ALMT proteins requires the presence of a specific amino acid motif in ALMTs that shares similarity with a GABA-binding site in mammalian GABAAreceptors. Here, we explore why TaALMT1-activation leads to a negative correlation between malate efflux and endogenous GABA concentrations ([GABA]i) in both wheat root tips and in heterologous expression systems. We show that TaALMT1 activation reduces [GABA]ibecause TaALMT1 facilitates GABA efflux. TaALMT1-expression also leads to GABA transport into cells, demonstrated by a yeast complementation assay and via14CGABA uptake into TaALMT1-expressingXenopus laevisoocytes; this was found to be a general feature of all ALMTs we examined. Mutation of the GABA motif (TaALMT1F213C) prevented both GABA influx and efflux, and uncoupled the relationship between malate efflux and [GABA]i. We conclude that ALMTs are likely to act as both GABA and anion transportersin planta. GABA and malate appear to interact with ALMTs in a complex manner regulating each other’s transport, suggestive of a role for ALMTs in communicating metabolic status.

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Temperature-dependent translational regulation of the ER omega-3 fatty acid desaturase gene in wheat root tips

The Plant Journal ◽

10.1046/j.1365-313x.2000.00925.x ◽

2000 ◽

Vol 24 (6) ◽

pp. 805-813 ◽

Cited By ~ 57

Author(s):

Gorou Horiguchi ◽

Takuichi Fuse ◽

Naoto Kawakami ◽

Hiroaki Kodama ◽

Koh Iba

Keyword(s):

Fatty Acid ◽

Translational Regulation ◽

Fatty Acid Desaturase ◽

Wheat Root ◽

Omega 3 ◽

Root Tips ◽

Temperature Dependent ◽

Desaturase Gene ◽

Omega 3 Fatty Acid ◽

Fatty Acid Desaturase Gene

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Histochemical Examination of Invertase Activities in the Growing Tip of the Plant Root

The Open Plant Science Journal ◽

10.2174/1874294701710010035 ◽

2017 ◽

Vol 10 (1) ◽

pp. 35-45

Author(s):

N.F. Lunkova ◽

N.A. Burmistrova ◽

M.S. Krasavina

Keyword(s):

Plant Root ◽

Invertase Activity ◽

Root Tip ◽

Elongation Zone ◽

Root Tips ◽

Phloem Unloading ◽

Meristem Cell ◽

Transition To Elongation ◽

Different Tissues

Background:A growing part of the root is one of the most active sinks for sucrose coming from source leaves through the phloem. In the root, sucrose is unloaded from conducting bundles and is distributed among the surrounding cells. To be involved in the metabolism, sucrose should disintegrate into hexoses by means of degrading enzymes.Aims:The aim of this research was to explore the possibility of the involvement of one such enzymes, invertase, in phloem unloading as well as distribution of its activity in the functionally different tissues of the plant root tips.Method:To estimate the enzyme activities in root tissues, we applied two techniques: the histochemical method using nitro blue tetrazolium. The localization of phloem unloading was studied with carboxyfluorescein, a fluorescent marker for symplastic transport.Results:Invertase activity was not detected in the apical part of the meristem. It appeared only between the basal part of this zone and the beginning of the elongation zone. There is the root phloem unloading in that area. Invertase activity increased with increasing the distance from the root tip and reached the highest values in the region of cell transition to elongation and in the elongation zone. The activities of the enzyme varied in different tissues of the same zone and sometimes in the neighboring cells of the same tissue. Biochemical determination of invertase activity was made in the maize root segments coincident to the zones of meristem, cell elongation and differentiation. The results of both methods of determination of invertase activity were in agreement.Conclusion:It was concluded that phloem unloading correlated with invertase activity, possibly because of the activation of invertase by unloaded sucrose. Invertase is one of the factors involved in the processes preparing the cells for their transition to elongation because the concentration of osmotically active hexoses increases after cleavage of sucrose, that stimulates water entry into the cells, which is necessary for elongation growth.

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The dieca effect in the respiration of barley

Proceedings of the Royal Society of London Series B Biological Sciences ◽

10.1098/rspb.1957.0052 ◽

1957 ◽

Vol 147 (928) ◽

pp. 309-315 ◽

Cited By ~ 4

Keyword(s):

Related Species ◽

Oxidation Mechanism ◽

Wheat Root ◽

Barley Root ◽

Root Tips ◽

Full Agreement ◽

Salt Uptake ◽

System A ◽

Simultaneous Comparison ◽

Independent Work

Results previously described for the respiration of barley root tips lead to the conclusion that their cytochrome system temporarily gives way to a copper-dependent system a few days after germination. Independent work with related species does not suggest similar effects. A simultaneous comparison of barley and wheat root tips has therefore been carried out and has given results in full agreement with previous work for both species. The change, referred to here as ‘the dieca effect’, occurs in barley and not in wheat. It indicates that a drastic alteration of oxidation mechanism may occur in a rapidly growing tissue without apparent disturbance to growth or salt uptake by the tissue.

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Genome-Wide Identification of Aluminum-Activated Malate Transporter (ALMT) Gene Family in Rubber Trees (Hevea brasiliensis) Highlights Their Involvement in Aluminum Detoxification

Forests ◽

10.3390/f11020142 ◽

2020 ◽

Vol 11 (2) ◽

pp. 142

Author(s):

Xiaowei Ma ◽

Feng An ◽

Lifeng Wang ◽

Dong Guo ◽

Guishui Xie ◽

...

Keyword(s):

Hevea Brasiliensis ◽

Phylogenetic Relationships ◽

Expression Patterns ◽

Rubber Tree ◽

Pcr Analysis ◽

Cis Elements ◽

Conserved Motifs ◽

Gene Structures ◽

Different Tissues ◽

Malate Transporter

The rubber tree (Hevea brasiliensis) is a widely cultivated crop in tropical acidic soil that is tolerant to high concentration of aluminum and the aluminum-activated malate transporter (ALMT) plays an important role in plant aluminum detoxification. However, the effects of ALMT on rubber tree aluminum tolerance, growth performance, and latex production are unclear. In this study, 17 HbALMT genes were identified from the genome of rubber trees. The physiological and biochemical characteristics, phylogenetic relationships, gene structures, conserved motifs, cis-elements of promoter, and expression patterns of the identified HbALMT genes were studied. Phylogenetic relationships indicated that these genes were divided into four clusters and genes in the same cluster have similar gene structures and conserved motifs. The promoters of HbALMT genes contain many cis-elements associated with biotic stress and abiotic stress. Quantitative real-time PCR analysis revealed HbALMTs showed various expression patterns in different tissues, indicating the functional diversity of HbALMT genes in different tissues of rubber trees. Transcriptome analysis and qRT-PCR assay showed that most of the HbALMT genes responded to aluminum stress, and among the 17 HbALMTs, HbALMT1, HbALMT2, HbALMT13, and HbALMT15 displayed higher expression levels in roots after two or five days of Al treatments, indicating their potential involvement in aluminum detoxification. Taken together, this study laid a foundation for further understanding the molecular evolution of the ALMT genes and their involvement in rubber tree aluminum adaption.

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