外生菌根真菌Paxillus involutus吸收Cd^(2+)及H_2O_2对Cd^(2+)内流的调控作用

【目的】本文研究了外生菌根真菌Paxillus involutus对Cd^(2+)的吸收作用以及H_2O_2对Cd^(2+)内流的调控作用。【方法】以Paxillus involutus的2种菌株MAJ和NAU为研究材料,利用50μmol/L Cd Cl2对材料进行24 h处理,应用非损伤微测技术测定菌丝的Cd^(2+)和Ca^(2+)离子流。【结果】结果显示,Cd^(2+)处理后,MAJ和NAU菌丝的Cd^(2+)内流增强,同时也显著促进了Ca^(2+)的内流。Ca^(2+)通道抑制剂(Verapamil、Gd Cl3、TEA)处理后,Cd^(2+)和Ca^(2+)内流强度均明显减弱,表明Cd^(2+)是通过钙通透性离子通道(Ca PCs)进入菌丝细胞的。Cd^(2+)处理促进了Cd^(2+)和Ca^(2+)的内流,很可能是Cd^(2+)激活了菌丝质膜的Ca PCs。Ca^(2+)和Cd^(2+)的竞争性实验结果显示,高浓度的Ca^(2+)抑制菌株MAJ和NAU的Cd^(2+)内流;反过来,测试液中Cd^(2+)浓度的提高也明显降低了Ca^(2+)的内流强度,这证明Ca^(2+)和Cd^(2+)是竞争性地通过Ca PCs进入菌丝细胞的。此外还发现,H_2O_2(1.0 mmol/L)能增强菌丝的Cd^(2+)和Ca^(2+)内流,而ROS清除剂DMTU却显著抑制了菌株对Ca^(2+)和Cd^(2+)的吸收,表明H_2O_2在调控菌丝细胞Ca PCs介导Cd^(2+)内流的过程中具有重要作用。【结论】综上,外生菌根真菌Paxillus involutus对Cd^(2+)具有富集作用并且可以通过H_2O_2激活Ca PCs促进Cd^(2+)内流。

Effect of NaCl on growth and ion relations in two salt-tolerant strains of Paxillus involutus

The effect of NaCl on growth, biomass and ion relations of two salt-tolerant isolates of Paxillus involutus, MAJ and NAU were investigated. The two Paxillus strains were exposed to the following concentrations of NaCl： 0, 100, 200 and 500 mmol·L^-1. Growth of MAJ and NAU was enhanced by 100 mmol·L^-1 NaCl but severely inhibited at the concentration of 500 mmol·L^-1. NAU exhibited a greater capacity to exclude Na^＋ and Cl^- under all salinity levels, whereas the salt-includer MAJ had a higher capacity in nutrient uptake under salt stress. The ratios Na^＋/K^＋, Na^＋/Ca^2＋ and Na^＋/Mg^2＋ in NaCl-treated MAJ and NAU did not increase at levels of 100 and 200 mmol·L^-1 NaCl but markedly increased at 500 mmol·L^-1. This suggests that the two strains, especially MAJ, enhanced nutrient uptake corresponding to the increased Na^＋ influx at moderate salinity. We conclude that both MAJ and NAU are able to tolerate 500 mmol·L^-1 NaCl but there are species-specific differences in retaining ionic homeostasis in the two Paxillus strains. NAU is a salt-excluder, MAJ is a salt-includer but retains a high capacity in nutrient selectivity under saline conditions. Their definite mechanisms to enhance salt tolerance of mycorrhizal hosts need further study.

Bioinformatics analysis of metallothionein gene from <i>Agaricus bisporus, Ganoderma lucidum, Taiwanofungus camphorates</i>and <i>Paxillus involutus</i>

Metallothionein (MT) gene has an important role in the detoxification of toxic metals especially some heavy metals. Based on the published sequences of MT genes from Agaricus bisporus, Garnoderma lucidum, Taiwanofungus camphoratus and Paxillus involutus as a type of the edible or medical mushroom in NCBI database, their molecular structures, physiological functions and evolutionary relationship were analyzed using the bioinformatics methods. Results showed that AbMT, GlMT, TcMT and PiMT genes contained complete open reading frame (ORF) and their theoretical points of the last three encoding proteins were higher than 7.0. AbMT, GlMT, TcMT and PiMT were relatively rich in random coil and extended strand, but transmembrane helices and signal peptides were not found. 4 MTs were mainly localized in cell nucleus (over 60%) and their cellular functions might have some relation to central intermediary metabolism. Multiple sequence alignment indicated relatively high identity (more than 52%) and short genetic distances (lower than 0.900) among 4 MT nucleotide sequences. Abundant genetic diversity and strong codon bias were found based on the halotype diversity, average number of nucleotide differences, nucleotide diversity, effective number of codons, codon bias index and scaled chisquare. Simultaneously, we deduced that 4 MT genes during molecular evolution were under positive selection. The present study might provide basis for further investigation of MTs molecular mechanisms and genetic laws.

盐胁迫下外生菌根菌Paxillus抗氧化酶活性的变化

[目的]通过测定2种菌株的抗氧化酶活性来研究其抗盐机理。[方法]以外生菌根真菌Paxillus involutus的2种菌株MAJ和NAU作为材料,研究在不同NaCl浓度(0、100、200、500 mmol/L)处理条件下抗氧化酶活性的变化。[结果]100 mmol/L NaCl可以促进菌株MAJ和NAU的增长及其生物量的增加;短期盐胁迫(1 d)诱导了菌株MAJ中SOD、CAT和POD活性的升高,但随着盐处理时间的延长,这些酶活性在100和200 mmol/L盐胁迫下均有所降低;而菌株NAU在长期盐胁迫(9 d)下能更好地维持各抗氧化酶活性,尤其是APX、GPX和POD。[结论]盐处理的菌株抗氧化酶活性明显高于对照菌株。