Blue Light Perception and Signal Transduction in Neurospora crassa

Abstract Heterotrimeric G proteins, consisting of α, β, and γ subunits, transduce environmental signals through coupling to plasma membrane-localized receptors. We previously reported that the filamentous fungus Neurospora crassa possesses a Gα protein, GNA-1, that is a member of the Gαi superfamily. Deletion of gna-1 leads to defects in apical extension, differentiation of asexual spores, sensitivity to hyperosmotic media, and female fertility. In addition, Δgna-1 strains have lower intracellular cAMP levels under conditions that promote morphological abnormalities. To further define the function of GNA-1 in signal transduction in N. crassa, we examined properties of strains with mutationally activated gna-1 alleles (R178C or Q204L) as the only source of GNA-1 protein. These mutations are predicted to inhibit the GTPase activity of GNA-1 and lead to constitutive signaling. In the sexual cycle, gna-1R178C and gna-1Q204L strains are female-fertile, but produce fewer and larger perithecia than wild type. During asexual development, gna-1R178C and gna-1Q204L strains elaborate abundant, long aerial hyphae, produce less conidia, and possess lower levels of carotenoid pigments in comparison to wild-type controls. Furthermore, gna-1R178C and gna-1Q204L strains are more sensitive to heat shock and exposure to hydrogen peroxide than wild-type strains, while Δgna-1 mutants are more resistant. In contrast to Δgna-1 mutants, gna-1R178C and gna-1Q204L strains have higher steady-state levels of cAMP than wild type. The results suggest that GNA-1 possesses several Gβγ-independent functions in N. crassa. We propose that GNA-1 mediates signal transduction pathway(s) that regulate aerial hyphae development and sensitivity to heat and oxidative stresses, possibly through modulation of cAMP levels.

Download Full-text

Blue and green are frequently seen: responses of seeds to short- and mid-wavelength light

Seed Science Research ◽

10.1017/s0960258511000444 ◽

2011 ◽

Vol 22 (1) ◽

pp. 27-35 ◽

Cited By ~ 9

Author(s):

Danica E. Goggin ◽

Kathryn J. Steadman

Keyword(s):

Blue Light ◽

Seedling Establishment ◽

Native Species ◽

Green Light ◽

Model System ◽

Light Perception ◽

Vegetative Tissues ◽

Wavelength Light

AbstractSeeds have long been a model system for studying the intricacies of phytochrome-mediated light perception and signalling. However, very little is known about how they perceive blue and green light. Cryptochromes and phototropins, the major blue-light receptors in plants, are increasingly well-studied in vegetative tissues, but their role in light perception in seeds largely remains a mystery. Green light elicits a number of responses in plants that cannot be explained by the action of any of the known photoreceptors, and some seeds are apparently also capable of perceiving green light. Here, the responses of seeds to blue and green light are collated from a thorough examination of the literature and considered from the perspective of the potential photoreceptor(s) mediating them. Knowledge of how seeds perceive wavelengths that are suboptimal for phytochrome activation could help to improve germination and seedling establishment for both crop and native species.

Download Full-text

Identification and Characterization of Genes Required for Cell-to-Cell Fusion in Neurospora crassa

Eukaryotic Cell ◽

10.1128/ec.05003-11 ◽

2011 ◽

Vol 10 (8) ◽

pp. 1100-1109 ◽

Cited By ~ 102

Author(s):

Ci Fu ◽

Priyadarshini Iyer ◽

Amrita Herkal ◽

Julia Abdullah ◽

Angela Stout ◽

...

Keyword(s):

Signal Transduction ◽

Transcription Factors ◽

Neurospora Crassa ◽

Cell Fusion ◽

Single Gene ◽

Vesicular Trafficking ◽

Screening Procedure ◽

Fusion Genes ◽

Fusion Event ◽

Screening Experiments

ABSTRACT A screening procedure was used to identify cell fusion (hyphal anastomosis) mutants in the Neurospora crassa single gene deletion library. Mutants with alterations in 24 cell fusion genes required for cell fusion between conidial anastomosis tubes (CATs) were identified and characterized. The cell fusion genes identified included 14 genes that are likely to function in signal transduction pathways needed for cell fusion to occur ( mik-1 , mek-1 , mak-1 , nrc-1 , mek-2 , mak-2 , rac-1 , pp2A , so/ham-1 , ham-2 , ham-3 , ham-5 , ham-9 , and mob3 ). The screening experiments also identified four transcription factors that are required for cell fusion ( adv-1 , ada-3 , rco-1 , and snf5 ). Three genes encoding proteins likely to be involved in the process of vesicular trafficking were also identified as needed for cell fusion during the screening ( amph-1 , ham-10 , pkr1 ). Three of the genes identified by the screening procedure, ham-6 , ham-7 , and ham-8 , encode proteins that might function in mediating the plasma membrane fusion event. Three of the putative signal transduction proteins, three of the transcription factors, the three putative vesicular trafficking proteins, and the three proteins that might function in mediating cell fusion had not been identified previously as required for cell fusion.

Download Full-text