Figure 1.
C. zeae-maydis requires light to form appressoria and infect maize.
A GUS-labeled reporter strain of C. zeae-maydis was inoculated on maize leaves, and incubated for four days in either A, 12 h light/dark cycles, or B, constant darkness. Black arrows indicate appressoria.
Figure 2.
Effects of light on cercosporin biosynthesis and conidiation of C. zeae-maydis.
A, Conidia (105) were spread on 0.2× PDA medium, and the plates were incubated for four days in constant white light, blue light (400–530 nm), red light (600–700 nm), or darkness. Cercosporin accumulated in the medium as a dark red pigment. B, Conidiation and cercosporin were measured after four days in cultures grown on V8-agar and 0.2× PDA, respectively.
Figure 3.
CRP1 encodes a putative ortholog of the N. crassa protein WC-1.
A, Conceptual translation of CRP1 revealed a protein predicted to contain at least four functional domains (LOV, PAS-Fold, PAS, and ZF) represented by shaded boxes. Diagrams of WC-1 and putative orthologs are presented to illustrate homology. Boxes with hash marks represent predicted low-complexity regions, NLS indicates a nuclear localization signal. B, Comparison of LOV domains from Crp1 of C. zeae-maydis and VVD of N. crassa. C, Alignment of the LOV domains encoded by vvd and putative wc-1 orthologs from fungi.
Figure 4.
Phylogenetic analysis of Crp1-like proteins.
Maximum likelihood tree inferred from Crp1-like proteins within the Zygomycota and the fungal subkingdom Dikarya. RAxML ML bootstrap values are represented by solid dots at each node where the value is above 80%.
Figure 5.
CRP1 regulates appressorium formation and stomatal tropism in C. zeae-maydis.
A, leaves inoculated with wild type, the Δcrp1-24 mutant, and Δcrp1-40 mutant were observed with electron microscopy. Stomata are indicated with black arrows. B, ratio of appressoria formed per stomate encountered for the wild type and Δcrp1 mutants. Ratio was calculated by counting how many appressoria were formed by 100 arbitrarily selected hypha that had physically encountered a stomate.
Figure 6.
CRP1 regulates lesion formation in C. zeae-maydis.
Maize leaves were inoculated with a suspension of conidia (105) of wild type or the Δcrp1-24 mutant, and the inoculated maize plants were incubated in the green house for 12 days. DAI = days after inoculation.
Figure 7.
A, Conidia (105) of wild type and Δcrp1-24 were inoculated on V8-agar medium, and incubated for four days in constant white, blue, red light, or darkness. B, Conidia produced by the wild type and CRP1 mutants grown on 0.2× PDA in constant white light for seven days.
Figure 8.
Disruption of CRP1 affects cercosporin biosynthesis.
A, Conidia (105) were spread on 0.2× PDA, and incubated for three days and seven days in constant white light. DAI = days after inoculation. B, Quantification of cercosporin biosynthesis in various light conditions. Cercosporin was measured from wild type and Δcrp1-24 cultures grown on 0.2× PDA in constant white, blue, red light and darkness for seven days.
Figure 9.
Ten-fold serial dilutions of conidia (103, 102, and 10) from each strain were inoculated on V8-agar medium, and exposed to UV light (3 mW/cm2, 90 min). After UV irradiation, the plates were placed in constant light for three days.
Figure 10.
Regulation of genes involved in photoreactivation by CRP1.
After exposure to UV light, cultures were incubated under white-light condition for 1 h to promote photoreactivation. The experiments were performed with three biological replicates, and two independent experiments produced similar results.