Roles of putative His-to-Asp signaling modules HPT-1 and RRG-2, on viability and sensitivity to osmotic and oxidative stresses in Neurospora crassa

Abstract

Neurospora crassa has a putative histidine phosphotransfer protein (HPT-1) that transfers signals from 11 histidine kinases to two putative response regulators (RRG-1 and RRG-2) in its histidine-to-aspartate phosphorelay system. The hpt-1 gene was successfully disrupted in the os-2 (MAP kinase gene) mutant, but not in the wild-type strain in this study. Crossing the resultant hpt-1; os-2 mutants with the wild-type or os-1 (histidine kinase gene) mutant strains produced no progeny with hpt-1 or os-1; hpt-1 mutation, strongly suggesting that hpt-1 is essential for growth unless downstream OS-2 is inactivated. hpt-1 mutation partially recovered the osmotic sensitivity of os-2 mutants, implying the involvement of yeast Skn7-like RRG-2 in osmoregulation. However, the rrg-2 disruption did not change the osmotic sensitivity of the wild-type strain and the os-2 mutant, suggesting that rrg-2 did not participate in the osmoregulation. Both rrg-2 and os-2 single mutation slightly increased sensitivity to t-butyl hydroperoxide, and rrg-2 and hpt-1 mutations increased the os-2 mutant's sensitivity. Although OS-1 is considered as a positive regulator of OS-2 MAP kinase, our results suggested that HPT-1 negatively regulated downstream MAP kinase cascade, and that OS-2 and RRG-2 probably participate independently in the oxidative stress response in N. crassa.

The Genomes of Three Uneven Siblings: Footprints of the Lifestyles of Three Trichoderma Species

“…For rim15, only minor growth effects were detected upon deletion, while SSK1 affects sexual development and SSK1 and SKN7 are responsible for stress resistance (735). Comparable functions were found for N. crassa RRs (737,738).…”

Master and Commander in Fungal Pathogens: the Two-Component System and the HOG Signaling Pathway

“…The ypdAϪ/ ypdAϩ heterokaryons show greater sensitivity to increased osmotic pressure, but not to H 2 O 2 , than the wild-type strain, indicating that YpdA is involved in the osmosensing signaling of A. nidulans (137). N. crassa has a Ypd1 homologue, named HPT-1 (histidine phosphotransfer protein 1), which also appears to be essential for viability because disruption of the hpt-1 gene is possible only in the os-2⌬ (Hog1 homologue) mutant background and not in the wild-type background (16). These data indicate that lethality caused by hpt-1 disruption is mediated through the Os-2 MAPK.…”

Characterization of NikA Histidine Kinase and Two Response Regulators with Special Reference to Osmotic Adaptation and Asexual Development inAspergillus nidulans

“…6,16) Similarly, it has been reported that RRG-1 (an SskA ortholog) is involved in the osmotic stress response, 24) while a mutant of RRG-2 (an SrrA ortholog) exhibits no sensitivity to high osmotic conditions. 25) In the case of C. heterostrophus, Dic1 is responsible for osmotic adaptation, and the deletion mutants of RRs (Áchssk1 and Áchskn7) show moderate sensitivity to osmotic stress. 19,22,26) It has also been suggested that the RRs ChSsk1 and ChSkn7 additively contribute to osmotic adaptation.…”