A maize‐specifically expressed gene cluster in Ustilago maydis

Abstract

Summary The corn pathogen Ustilago maydis requires its host plant maize for development and completion of its sexual cycle. We have identified the fungal mig2–1 gene as being specifically expressed during this biotrophic stage. Intriguingly, mig2–1 is part of a gene cluster comprising five highly homologous and similarly regulated genes designated mig2–1 to mig2–5. Deletion analysis of the mig2–1 promoter provides evidence for negative and positive regulation. The predicted polypeptides of all five genes lack significant homologies to known genes but have characteristic N‐terminal secretion sequences. The secretion signals of mig2–1 and mig2–5 were shown to be functional, and secretion of a full length Mig2–1‐eGFP fusion protein to the extracellular space was demonstrated. The central domains of the Mig2 proteins are highly variable whereas the C‐termini are strongly conserved and share a characteristic pattern of eight cysteine residues. The mig2 gene cluster was conserved in a wide collection of U. maydis strains. Interestingly, some U. maydis isolates from South America had lost the mig2–4 gene as a result of a homologous recombination event. Furthermore, the related Ustilago scitaminea strain, which is pathogenic on sugar cane, appears to lack the mig2 cluster. We describe a model of how the mig2 cluster might have evolved and discuss its possible role in governing host interaction.

Genome Comparison of Barley and Maize Smut Fungi Reveals Targeted Loss of RNA Silencing Components and Species-Specific Presence of Transposable Elements

“…The largest class of U. hordei effectors contained 19 Mig1-related proteins having a characteristic and conserved pattern of Cys residues. In U. maydis, Mig1 was shown to be highly induced during biotrophic growth in maize (Basse et al, 2002). U. maydis has only three copies of Mig1-like genes, while eight copies exist in S. reilianum (see Supplemental Figure 10 online; Schirawski et al, 2010).…”

Dissecting Defense-Related and Developmental Transcriptional Responses of Maize during Ustilago maydis Infection and Subsequent Tumor Formation

“…The ip gene (Broomfield and Hargreaves, 1992) is constitutively expressed and allows quantification of the overall presence of the fungus. Expression of mig2-5, which is strictly linked to biotrophic growth (Basse et al, 2002a), provides for a suitable marker for the fungal presence within plant tissue. Transcript levels of mig2-5 were comparable in samples T1 and T3 were reduced in sample T2 and lowest in T4 (Fig.…”

“…Gene-specific primer combinations were used to determine expression of mig2-5 (m25gsa/m25gsb; Basse et al, 2002a) and Umi2 (5#-CCATATCTCACTAC-CAAAAGCATCCGATCC-3#/5#-GTTCCAACCCTTCGAAAAAGTGGTGCG-3#). The primers designed against the Umi2 sequence did not match the sequence of the homologous TPS5 gene.…”

“…To address the interplay between U. maydis and its host, differential display analysis was performed comparing expression in leaf tumor and noninfected leaf tissue . The fungal genes retrieved from this approach were mig1 and mig2-1 to mig2-5, which display a pronounced plant-specific expression profile and encode small, secreted, Cys-containing proteins of unknown function, as well as udh1, which encodes a functional steroid 5a-reductase (Basse et al, , 2002a(Basse et al, , 2002bFarfsing et al, 2005). Here, I report the identification of maize genes that exhibit a marked differential expression profile during U. maydis infection.…”

Expression of effector gene SIX1 of Fusarium oxysporum requires living plant cells

“…For Avr9 and Mpg1 it was shown that expression (partly) depends on a general nitrogen response factors (NRF1 and NPR1, respectively) (Lau and Hamer, 1996;Perez-Garcia et al, 2001;Soanes et al, 2002). However, expression of other in planta induced genes does not respond to changes in nitrogen availability, for example AVR4, ECP1 and ECP2 (C. fulvum), AvrLm1 (Leptosphaeria maculans), MIG1 and the MIG2 gene cluster (Ustilago maydis) (Basse et al, 2002(Basse et al, , 2000Gout et al, 2006;Van den Ackerveken et al, 1994;Wubben et al, 1994). Even for the genes that are expressed in an environment with limited nitrogen, it is not known which circumstances induce expression in planta, since there are indications that within the host plant, nitrogen is not limiting Oliver, 2001, 2002).…”