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Reducing Cytoplasmic Polyamine Oxidase Activity in Arabidopsis Increases Salt and Drought Tolerance by Reducing Reactive Oxygen Species Production and Increasing Defense Gene Expression.

ABSTRACT: Arabidopsis thaliana polyamine oxidase 5 gene (AtPAO5) functions as a thermospermine (T-Spm) oxidase. Aerial growth of its knock-out mutant (Atpao5-2) is significantly repressed by low dose(s) of T-Spm but not by other polyamines. Massive analysis of 3’-cDNA ends (MACE) was performed. Cell wall, lipid and secondary metabolisms were dramatically affected in low dose T-Spm-treated Atpao5-2. Intriguingly Fe-deficient responsive genes and drought stress-induced genes were up-regulated, suggesting that vascular system loses the function. Histological observation showed that vascular system of the joint part between stem and leaves was structurally destroyed. The results indicate that T-Spm homeostasis by a balance of synthesis and catabolism, catalysed by AtPAO5 in Arabidopsis, is important for maintaining vascular system. Phylogenetic analysis showed that PAOs from vascular plants are classified into four clades (I-IV) and AtPAO5 belongs to the clade III. Clade III members show high identity to metazoan PAOs and are not found in non-vascular plants. Furthermore, all the clade III genes are intron-less or contain a single intron whereas the other three clade genes usually contain 7 to 9 introns. The data suggest the occurrence of a horizontal gene transfer of ancestral clade III PAO gene(s) from primitive animals. Fine tuning of T-Spm metabolism is critical for vascular plants and its catabolic gene was acquired from a certain Metazoan to equip the vascular system.

ORGANISM(S): Arabidopsis thaliana

PROVIDER: GSE69510 | GEO | 2016/02/22

SECONDARY ACCESSION(S): PRJNA285758

REPOSITORIES: GEO

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Project description:Fruits of transgenic tomato (Solanum lycopersicum) plants engineered with ripening-induced, yeast S-adenosylmethionine decarboxylase (ySAMdc) gene, accumulate the higher polyamines spermidine (Spd) and spermine (Spm) and demonstrate ameliorated phytonutrient content, juice quality, and prolonged vine life. Enhanced nitrogen-carbon interactions were revealed by comprehensive Nuclear Magnetic Resonance (NMR) spectroscopy-based metabolite profiling of the transgenics, suggesting that Spd and Spm are perceived as nitrogenous metabolites by the fruit cells (Mattoo et al., 2006). The recent work by our colleagues identified the effects of Spd/Spm accumulation on various functional classes of tomato genes affected during ripening by probing 1522 ESTs on a custom-made array (Srivastava et al., 2007). In this study we monitored alterations of genome-wide transcriptional patterns in pericarp of Spd/Spm-accumulating tomatoes by means of direct comparison with azygous controls using DNA-microarray technology. Consistent with the ySAMdc expression pattern, very minor transcriptional alterations were detected in mature green developmental stage. For both breaker and red stages, large mutual and unique gene sets displayed altered levels of transcript. Ontological term analysis of up- and down-regulated transcript groups revealed processes in cell metabolism that are regulated by increased levels of Spd/Spm in ripening tomato fruits. These processes mainly involve carbohydrate and amino acids metabolism and protein synthesis. Additionally, transcript levels of representative genes encoding structural enzymes for related biosynthetic pathways show strong relationship to specific metabolites that were identified as regulated in Spd/Spm-accumulating transgenics. Plants of both genotypes were grown in randomized blocks (3 blockes 8-10 plants each). At each of 3 developmental stages (mature green, breaker and pink-red) a single fruit was harvested from a randomly chosen plant of each genotype within each block. In each harvest different plants in each block were taken to represent each genotype. Following harvest, equal pericarp samples were cut from the equator region of each fruit. These samples were pooled according to genotype prior to RNA extraction, allowing equal representation of each block in the final sample. A total of 3 harvests taken from each genotype were eventually analyzed– each harvest representing a biological repeat.

Project description:Photosynthetic organisms use sunlight as energy source but rely on respiration during the night and in non-photosynthetic tissues. Respiration is also active in photosynthetically active cells, where its role is still unclear due to a lack of viable mutants. We previously isolated plants lacking a functional complex I (ndufa5). Plants lacking cytochrome c oxidase (complex IV) activity are generally lethal but were here isolated exploiting the possibility of generating knockout lines through vegetative propagation in the moss Physcomitrium patens. ndufa5 plants showed alterations in carbon and nitrogen metabolism that are consistent with those reported in other Complex I mutants in vascular plants. One of the general features of Complex I-deficient plants, that was observed also in ndufa5, is the induction of the alternative oxidase (AOX). We found the metabolic alterations and the AOX induction in ndufa5 to be more severe by the end of the night than during day. The transcriptome of ndufa5 plants suggests that mitochondria-to-nucleus retrograde signalling pathways are strongly induced by the end of the night, which are probably mediated by a homolog of the transcription factor ANAC017, described in vascular plants. cox11 mutants showed severely impaired growth, with an altered composition of the respiratory apparatus and increased electron transfer through the alternative oxidase. The light phase of photosynthesis remained largely unaffected while the efficiency of carbon fixation was moderately reduced. Transcriptomic and metabolomic analyses showed that the disruption of the cytochrome pathway had broad consequences for carbon and nitrogen metabolism. A major alteration in nitrogen assimilation was observed with a general reduction in amino acid abundance. A partial rescue of the growth could be obtained by growing the plants with an external supply of amino acids but not with sugars, demonstrating that respiration in plant photosynthetic cells plays an essential role at the interface between carbon and nitrogen metabolism and a key role in providing carbon skeletons for amino acid biosynthesis.

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Reducing Cytoplasmic Polyamine Oxidase Activity in Arabidopsis Increases Salt and Drought Tolerance by Reducing Reactive Oxygen Species Production and Increasing Defense Gene Expression.

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