Construction of a Constitutively Activated Gα Mutant in the Maize Pathogen <i>Cochliobolus heterostrophus</i>

Abstract

Conserved eukaryotic signaling proteins participate in development and disease in plant pathogenic fungi. Mutants in CGA1, a heterotrimeric G protein G subunit gene of the maize pathogen Cochliobolus heterostrophus, are defective in several developmental pathways. Conidia from CGA1 mutants germinate as abnormal, straight-growing germ tubes that form few appressoria, and the mutants are female-sterile. The CGA1, Gα subunit, is also thought to act as a down regulator of hydrophobin expression and secretion in this fungus and in related Ascomycete species. Although cga1 mutants can cause normal lesions on plants there are host physiology conditions under which full virulence requires signal transduction through CGA1-mediated pathways. A Gα activated mutant, cga1 Q204L was created to help establish the role of CGA1 in growth and development, and in mediating hydrophobin secretion and expression. The activated Gα allele was transformed into a cga1 mutant strain. The transgenic lines showed phenotypes resembling the null mutant in development, sporulation and hydrophobicity, indicating a possible role for CGA1 as a stabilizer of these traits.

Gene Expression Modulation of Two Biosynthesis Pathways via Signal Transduction in <i>Cochliobolus heterostrophus</i>

“…At the output of these cascades are sets of target genes, whose study of expression has begun in recent years. We previously identified roles for the individual G-protein Gα and Gβ subunits [1]- [3] [5] [6] and for MAPK [4] [11] in C. heterostrophus development, reproduction and pathogenicity (summarized in [5]). To date, little knowledge exists on downstream signaling elements of these cascades in this species.…”

“…In Cochliobolus heterostrophus, the agent of Southern Corn Leaf Blight, Gα1 (CGA1) and Gβ (CGB1) subunits, as well as of a mitogen-activated protein kinase (MAPK, CHK1), participates in several developmental pathways. Disruption studies of these signaling components results in severe phenotypes, including loss of the normal meandering hyphal growth pattern on hard surfaces, lack of appressorium formation, and defects in mating and virulence [1]- [6]. Both GTP-Gα and free Gβγ can activate downstream targets [7], and an epistatic relationship may exist between the two branches of the G-protein pathway [5].…”

Efficiency of Botanical and Chemical Pesticides on the Control of Field Insect Pests under Cowpea Production

“…This botanical concoction has been registered in Uganda by the Ministry of Agriculture, Animal Industry and Fisheries (MAAIF) [60]. Pongamia pinnata (also known as Karanj) is a tropical tree native to southeast Asia [61], its oil is rich in medicinal properties and can be used as a biopesticide and insect repellent [61]. Although its seeds are highly rich in ricinoleic acid, a polyunsaturated fatty acidharvested for industrial work [62], Ricinus communisis a castor bean plant whose toxicity is attributed to the presence of ricin, a water-soluble glycoprotein concentrated in seed endosperm but does not partition in seed oil [63] and is found in lesser concentration in other plant parts.…”

Pathogenicity Assay for <i>Cochliobolus heterostrophus</i> G-Protein and MAPK Signaling Deficiency Strains

“…Mutants in C. heterostrophus cga1 produce conidia that germinate as abnormal, straight-growing germ tubes forming few appressoria [6] [10]. A Gα activated mutant, cga1 Q204L , showed phenotypes resembling the null mutant in development, sporulation and hydrophobicity, indicating a possible role for cga1 as a stabilizer of these traits [14]. Nevertheless, the cga1 mutants can cause normal lesions on plants, unlike other filamentous fungal plant pathogens in which functional homologues of cga1 are required for full virulence [6].…”