ABSTRACT
Amino acids play a crucial role in the growth and development of insects. Aphids cannot ingest enough amino acids in plant phloem to meet their requirements, and therefore, they are mainly dependent on the obligate symbiont Buchnera aphidicola to synthesize essential amino acids. Besides Buchnera, aphids may harbor another facultative symbiont, Arsenophonus, which alters the requirement of the cotton-melon aphid Aphis gossypii for amino acid. However, it is unclear how Arsenophonus regulates the requirement. Here, we found that Arsenophonus ameliorated growth performance of A. gossypii on an amino acid-deficient diet. A deficiency in lysine (Lys) or methionine (Met) led to changes in the abundance of Arsenophonus. Arsenophonus suppressed the abundance of Buchnera when aphids were fed a normal amino acid diet, but this suppression was eliminated or reversed when aphids were on a Lys- or Met-deficient diet. The relative abundance of Arsenophonus was positively correlated with that of Buchnera, but neither of them was correlated with the body weight of aphids. The relative expression levels of Lys and Met synthase genes of Buchnera were affected by the interaction between Arsenophonus infections and Buchnera abundance, especially in aphids reared on a Lys- or Met-deficient diet. Arsenophonus coexisted with Buchnera in bacteriocytes, which strengthens the interaction. IMPORTANCE The obligate symbiont Buchnera can synthesize amino acids for aphids. In this study, we found that a facultative symbiont, Arsenophonus, can help improve aphids' growth performance under amino acid deficiency stress by changing the relative abundance of Buchnera and the expression levels of amino acid synthase genes. This study highlights the interaction between Arsenophonus and Buchnera to ameliorate aphid growth under amino acid stress.
Subject(s)
Aphids , Buchnera , Gammaproteobacteria , Animals , Buchnera/genetics , Aphids/physiology , Amino Acids , Symbiosis , Methionine , LysineABSTRACT
To avoid zinc (Zn) toxicity, plants have developed a Zn homeostasis mechanism to cope with Zn excess in the surrounding soil. In this report, we uncovered the difference of a cross-homeostasis system between iron (Fe) and Zn in dealing with Zn excess in the Zn hyperaccumulator Arabidopsis halleri ssp. gemmifera and nonhyperaccumulator Arabidopsis thaliana. Arabidopsis halleri shows low expression of the Fe acquisition and deficiency response-related genes IRT1 and IRT2 compared with A. thaliana. In A. thaliana, lowering the expression of IRT1 and IRT2 through the addition of excess Fe to the medium increases Zn tolerance. Excess Zn induces significant Fe deficiency in A. thaliana and reduces Fe accumulation in shoots. By contrast, the accumulation of Fe in shoots of A. halleri was stable under various Zn treatments. Root ferric chelate reductase (FRO) activity and expression of FIT are low in A. halleri compared with A. thaliana. Overexpressing a ZIP family member IRT3 in irt1-1, rescues the Fe-deficient phenotype. A fine-tuned Fe homeostasis mechanism in A. halleri maintains optimum Fe level by Zn-regulated ZIP transporters and prevents high Zn uptake through Fe-regulated metal transporters, and in part be responsible for Zn tolerance.
Subject(s)
Adaptation, Physiological/drug effects , Arabidopsis Proteins/genetics , Arabidopsis/genetics , Gene Expression Profiling , Gene Expression Regulation, Plant/drug effects , Iron/pharmacology , Membrane Transport Proteins/genetics , Zinc/toxicity , Adaptation, Physiological/genetics , Arabidopsis/drug effects , Arabidopsis/growth & development , Arabidopsis Proteins/metabolism , Basic Helix-Loop-Helix Transcription Factors/genetics , Basic Helix-Loop-Helix Transcription Factors/metabolism , Cation Transport Proteins/genetics , Cation Transport Proteins/metabolism , FMN Reductase/genetics , FMN Reductase/metabolism , Genes, Plant , Membrane Transport Proteins/drug effects , Plant Proteins/genetics , Plant Proteins/metabolism , Plant Roots/drug effects , Plant Roots/genetics , Plant Roots/metabolism , Plant Shoots/drug effects , Plant Shoots/genetics , Plant Shoots/metabolism , Reverse Transcriptase Polymerase Chain Reaction , Stress, Physiological/drug effects , Stress, Physiological/geneticsABSTRACT
OBJECTIVE: To further study the safety and effect of the umbilical cord blood (UCB)-derived mesenchymal stem cells (MSCs) on apoptosis of human cardiac myocyte (HCM). METHODS: The UCB was collected at the time of delivery with informed consent obtained from 10 donors. The UCB-derived MSCs was treated with 5-azaserine (5-AZA), and further introduced differentiation into cardiomyocytes. The telomerase activity, G-banding patterns of chromosomal karyotypes, tumor formation in nude mice, reverse transcription polymerase chain reaction (RT-PCR), and the inhibited apoptosis of UCB-derived MSCs were further investigated. This study was carried out in the laboratory of Beijing Shijitan Hospital, Beijing, China and Inheritance Research Section of Chinese Medical Institute, Beijing, China from July 2005 to December 2007. RESULTS: The MSCs-derived from UCB were differentiated into cardiomyocytes in vitro, possessed telomerase activity after 5-AZA induction, and no abnormal chromosomal karyotypes were observed. Expression of p53, cyclinA, cdk2, -actin, C-fos, h-TERT and c-myc were similar in MSCs before and after 5-AZA treatment. There was no tumor formation injected into nude mice. The UCB-derived MSCs significantly inhibited apoptosis of human cardiomyocytes. CONCLUSION: Umbilical cord blood-derived MSCs are safe and effective source of cell-transplantation treatment, and can inhibit the apoptosis of human cardiomyocytes in co-cultured.
Subject(s)
Apoptosis , Azaserine/pharmacology , Fetal Blood/cytology , Mesenchymal Stem Cells/drug effects , Myocardium/cytology , Animals , Humans , Karyotyping , Mesenchymal Stem Cells/cytology , Mice , Mice, NudeABSTRACT
ZIP transporters (ZRT, IRT-like proteins) are involved in the transport of iron (Fe), zinc (Zn) and other divalent metal cations. The expression of IRT3, a ZIP transporter, is higher in the Zn/cadmium (Cd) hyperaccumulator Arabidopsis halleri than is that of its ortholog in Arabidopsis thaliana, which implies a positive association of its expression with Zn accumulation in A. halleri. IRT3 genes from both A. halleri and A. thaliana functionally complemented the Zn uptake mutant Spzrt1 in Schizosaccharomyces pombe; and Zn uptake double mutant zrt1zrt2, Fe-uptake mutant fet3fet4 and conferred Zn and Fe uptake activity in Saccharomyces cerevisiae. By contrast, the manganese (Mn) uptake mutant smf1 phenotypes were not rescued. Insufficient Cd uptake for toxicity was found. Expression of IRT3-green fluorescent protein (GFP) fusion proteins in Arabidopsis root protoplasts indicated localization of both IRT3 proteins in the plasma membrane. Overexpressing AtIRT3 in A. thaliana led to increased accumulation of Zn in the shoot and Fe in the root of transgenic lines. Therefore, IRT3 functions as a Zn and Fe-uptake transporter in Arabidopsis.
