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Iron is an essential element for nearly all cells and limited iron availability often restricts growth. However, excess iron can also be deleterious, particularly when cells expressing high affinity iron uptake systems transition to iron rich environments. B acillus subtilis expresses numerous iron importers, but iron efflux has not been reported. Here, we describe the B. subtilis PfeT protein (formerly YkvW/ ZosA) as a P1B4-type ATPase in the PerR regulon that serves as an Fe( II) efflux pump and protects cells against iron intoxication. Iron and manganese homeostasis in B. subtilis are closely intertwined: a pfe T mutant is iron sensitive, and this sensitivity can be suppressed by low levels of Mn( II). Conversely, a pfe T mutant is more resistant to Mn( II) overload. In vitro, the PfeT ATPase is activated by both Fe( II) and Co( II), although only Fe( II) efflux is physiologically relevant in wild-type cells, and null mutants accumulate elevated levels of intracellular iron. Genetic studies indicate that PfeT together with the ferric uptake repressor (Fur) cooperate to prevent iron intoxication, with iron sequestration by the MrgA mini-ferritin playing a secondary role. Protection against iron toxicity may also be a key role for related P1B4-type ATPases previously implicated in bacterial pathogenesis. [ABSTRACT FROM AUTHOR]

Improving the drought resistance of rice is of great significance for expanding the planting area and improving the stable yield of rice. In our previous work, we found that ROLLED AND ERECT LEAF1 (REL1) protein promoted enhanced tolerance to drought stress by eliminating reactive oxygen species (ROS) levels and triggering the abscisic acid (ABA) response. However, the mechanism through which REL1 regulates drought tolerance by removing ROS is unclear. In this study, we identified REL1 interacting protein 5 (RIP5) and found that it directly combines with REL1 in the chloroplast. We found that RIP5 was strongly expressed in ZH11 under drought-stress conditions, and that the rip5-ko mutants significantly improved the tolerance of rice plants to drought, whereas overexpression of RIP5 resulted in greater susceptibility to drought. Further investigation suggested that RIP5 negatively regulated drought tolerance in rice by decreasing the content of ascorbic acid (AsA), thereby reducing ROS clearance. RNA sequencing showed that the knockout of RIP5 caused differential gene expression that is chiefly associated with ascorbate and aldarate metabolism. Furthermore, multiple experimental results suggest that REL1 is involved in regulating drought tolerance by inhibiting RIP5. Collectively, our findings reveal the importance of the inhibition of RIP5 by REL1 in affecting the rice's response to drought stress. This work not only explains the drought tolerance mechanism of rice, but will also help to improve the drought tolerance of rice. [ABSTRACT FROM AUTHOR]

Abstract: An extremely thermostable xylanaseB gene from hyperthermophilic bacterium Thermotoga maritima was ligated to pGHE vector and expressed in filamentous fungus Aspergillus niger. The vector was constructed using endogenous strong gla promoter, signal sequence, and pro-sequence (NVISKR). Positive transformants of the expression vector secreted XynB with thermostable characteristics, and optimal temperature >90°C. Yield of XynB in shaking culture reached ∼0.5g/l. Maximal enzymatic activity occurred at day 6, and was recorded as 625U/ml fermentation supernatant in a transformant using Remazol Brilliant Blue R-D-Xylan as substrate. mRNA levels of gla, bip, and hac1 between recombinant and control strain were detected by quantitative reverse transcription PCR. None of these three genes was regulated in the strain of xynB integration, indicating that high expression of XynB did not induce unfolded protein response. [Copyright &y& Elsevier]

An astaxanthin-overproducing (∼1000 μg g) strain of Phaffia rhodozyma, termed MK19, was established through 1-methyl-3-nitro-1-nitrosoguanidine and Co60 mutagenesis from wild-type JCM9042 (merely 35-67 μg g). The total fatty acid content of MK19 was much lower than that of the wild type. Possible causes of the astaxanthin increase were studied at the gene expression level. The expression of the carotenogenic genes crtE, crtI, pbs, and ast, which are responsible for astaxanthin biosynthesis from geranylgeranyl pyrophosphate, was highly induced at the mRNA level, leading to excessive astaxanthin accumulation. In contrast, transcription levels of the genes ( hmgs, hmgr, idi, mvk, mpd, fps), responsible for the initial steps in the terpenoid pathway, were essentially the same in wild type and MK19. Although fatty acid and total ergosterol content were reduced by 40-70 mg g and 760.3 μg g, respectively, in MK19 as compared with the wild type, but the transcription levels of rate-limiting genes in fatty acid and ergosterol pathways such as acc and sqs were similar. Because fatty acids and ergosterol are two branch pathways of astaxanthin biosynthesis in P. rhodozyma, our findings indicate that enhancement of astaxanthin in MK19 results from decreased fatty acid and ergosterol biosynthesis, leading to precursor accumulation, and transfer to the astaxanthin pathway. Strengthening of the mevalonate pathway is suggested as a promising metabolic engineering approach for further astaxanthin enhancement in MK19. [ABSTRACT FROM AUTHOR]