Yeast AP-1 like transcription factors (Yap) and stress response: a current overview

The mitochondrial iron exporter genes MMT1 and MMT2 in yeast are transcriptionally regulated by Aft1 and Yap1

Budding yeast (Saccharomyces cerevisiae) responds to low cytosolic iron by up-regulating the expression of iron import genes; iron import can reflect iron transport into the cytosol or mitochondria. Mmt1 and Mmt2 are nuclearly encoded mitochondrial proteins that export iron from the mitochondria into the cytosol. Here we report that MMT1 and MMT2 expression is transcriptionally regulated by two pathways: the low-iron-sensing transcription factor Aft1 and the oxidant-sensing transcription factor Yap1. We determined that MMT1 and MMT2 expression is increased under low-iron conditions and decreased when mitochondrial iron import is increased through overexpression of the high-affinity mitochondrial iron importer Mrs3. Moreover, loss of iron-sulfur cluster synthesis induced expression of MMT1 and MMT2 We show that exposure to the oxidant H2O2 induced MMT1 expression but not MMT2 expression and identified the transcription factor Yap1 as being involved in oxidant-mediated MMT1 expression. We defined Aft1- and Yap1-dependent transcriptional sites in the MMT1 promoter that are necessary for low-iron- or oxidant-mediated MMT1 expression. We also found that the MMT2 promoter contains domains that are important for regulating its expression under low-iron conditions, including an upstream region that appears to partially repress expression under low-iron conditions. Our findings reveal that MMT1 and MMT2 are induced under low-iron conditions and that the low-iron regulator Aft1 is required for this induction. We further uncover an Aft1-binding site in the MMT1 promoter sufficient for inducing MMT1 transcription and identify an MMT2 promoter region required for low iron induction.

Transcriptional and epigenetic control of regulated cell death in yeast

Unicellular organisms like yeast can undergo controlled demise in a manner that is partly reminiscent of mammalian cell death. This is true at the levels of both mechanistic and functional conservation. Yeast offers the combination of unparalleled genetic amenability and a comparatively simple biology to understand both the regulation and evolution of cell death. In this minireview, we address the capacity of the nucleus as a regulatory hub during yeast regulated cell death (RCD), which is becoming an increasingly central question in yeast RCD research. In particular, we explore and critically discuss the available data on stressors and signals that specifically impinge on the nucleus. Moreover, we also analyze the current knowledge on nuclear factors as well as on transcriptional control and epigenetic events that orchestrate yeast RCD. Altogether we conclude that the functional significance of the nucleus for yeast RCD in undisputable, but that further exploration beyond correlative work is necessary to disentangle the role of nuclear events in the regulatory network.

The Evolutionary and Molecular Features of Broad Host-Range Necrotrophy in Plant Pathogenic Fungi

Necrotrophic fungal pathogens cause considerable disease on numerous economically important crops. Some of these pathogens are specialized to one or a few closely related plant species, whereas others are pathogenic on many unrelated hosts. The evolutionary and molecular bases of broad host-range necrotrophy in plant pathogens are not very well-defined and form an on-going area of research. In this review, we discuss what is known about broad host-range necrotrophic pathogens and compare them with their narrow host-range counterparts. We discuss the evolutionary processes associated with host generalism, and highlight common molecular features of the broad host-range necrotrophic lifestyle, such as fine-tuning of host pH, modulation of host reactive oxygen species and metabolic degradation of diverse host antimicrobials. We conclude that broad host-range necrotrophic plant pathogens have evolved a range of diverse and sometimes convergent responses to a similar selective regime governed by interactions with a highly heterogeneous host landscape.

Highly Efficient Synthesis of Glutathione via a Genetic Engineering Enzymatic Method Coupled with Yeast ATP Generation

Glutathione is a tripeptide compound with many important physiological functions. A new, two-step reaction system has been developed to efficiently synthesize glutathione. In the first step, glutamate and cysteine are condensed to glutamyl-cysteine by endogenous yeast enzymes inside the yeast cell, while consuming ATP. In the second step, the yeast cell membrane is lysed by the permeabilizing agent CTAB (cetyltrimethylammonium bromide) to release the glutamyl-cysteine, upon which added glutathione synthetase converts the glutamyl-cysteine and added glycine into glutathione. The ATP needed for this conversion is supplied by the permeabilized yeast cells of glycolytic pathway. This method provided sufficient ATP, and reduced the feedback inhibition of glutathione for the first-step enzymatic reaction, thereby improving the catalytic efficiency of the enzyme reaction. In addition, the formation of suitable oxidative stress environment in the reaction system can further promote glutathione synthesis. By HPLC analysis of the glutathione, it was found that 2.1 g/L reduced glutathione is produced and 17.5 g/L oxidized glutathione. Therefore, the new reaction system not only increases the total glutathione, but also facilitates the subsequent separation and purification due to the larger proportion of oxidized glutathione in the reaction system.