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

Abstract

Infection of maize (Zea mays) plants with the smut fungus Ustilago maydis triggers the formation of tumors on aerial parts in which the fungal life cycle is completed. A differential display screen was performed to gain insight into transcriptional changes of the host response. Some of the genes strongly up-regulated in tumors showed a pronounced developmental expression pattern with decreasing transcript levels from basal to apical shoot segments, suggesting that U. maydis has the capacity to extend the undifferentiated state of maize plants. Differentially expressed genes implicated in secondary metabolism were Bx1, involved in biosynthesis of the cyclic hydroxamic acid 2,4-dihydroxy-7-methoxy-2H-1,4-benzoxazin-3-one, and a novel putative sesquiterpene cyclase gene U. maydis induced (Umi)2. Together with the up-regulation of Umi11 encoding a cyclotide-like protein this suggests a nonconventional induction of plant defenses. Explicitly, U. maydis was resistant to 2,4-dihydroxy-7-methoxy-2H-1,4-benzoxazin-3-one but susceptible to its benzoxazolinone derivative 6-methoxy-2-benzoxazolinone. Infection studies of isolated leaves with U. maydis and Colletotrichum graminicola provided evidence for coregulation of Umi2 and PR-1 gene expression, with mRNA levels strongly determined by the extent of fungal colonization within tissue. However, in contrast to Umi2, transcript levels of PR-1 remained low in plants infected with wild-type U. maydis but were 8-fold elevated upon infection with an U. maydis mutant strongly attenuated in pathogenic development. This suggests that U. maydis colonization in planta suppresses a classical defense response. Furthermore, comparative expression analysis uncovered distinct transcriptional programs operating in the host in response to fungal infection and subsequent tumor formation.

Signals that stop the rot: Regulation of secondary metabolite defences in cereals

“…Likewise, zealexin production is preceded by increased expression of the biosynthetic genes Tps6/11 [28]. Expression of both the Tps6 and Tps11 alleles have also been stimulated following U. maydis infection [18] and when silenced using VIGS, plants are more susceptible to U. maydis [103]. Taken together, these results propose that the plant hormones JA and Et mediate production of terpenoid phytoalexins and thereby defence in maize (Table 1).…”

“…northern and southern corn leaf blight and corn smut), and insect pests (i.e. the European corn borer and the maize plant louse) [15][16][17][18].…”

“…It has been shown that DIMBOA confers resistance to several maize pests including O. nubilalis and maize plant louse (Rhophalosiphum maydis) [15,16]. Additionally, resistance to fungal infections such as northern and southern corn leaf blight (caused by Helminthosporium turcicum and Bipolaris maydis respectively) as well as Ustilago maydis are well documented [15,17,18]. Ahmad et al (2011) proposed that DIMBOA is also involved in penetration resistance, independent of tissue damage, which challenges the classical mode of action accepted for BXs in maize [5].…”

Tandem mass spectrometry for the detection of plant pathogenic fungi and the effects of database composition on protein inferences

“…These pathogens were selected because: (i) pure cultures could be obtained, (ii) they are taxonomically distinct, (iii) they attack economically important crops, (iv) they infect different parts of plants, and (v) there is variation in the amounts of available genome and protein sequence information available for these pathogens. Specifically, U. maydis is a Basidiomycetes fungus that infects maize kernels [24] and its genome has been sequenced and well-annotated (http://www.broad.mit.edu/annotation/genome/ustilago_maydis/Home.html). F. graminearum is an Ascomycetes fungus that causes wheat head blight [25] and P. sojae is an Oomycetes pathogen that causes root and stem rot on soybean [26].…”

Identification of Wood Decay Related Genes fromPiptoporus Betulinus(Bull. Fr.) Karsten Using Differential Display Reverse Transcription PCR (DDRT-PCR)

“…To determine which genes are differentially expressed, comprehensive analysis is essential. this can be achieved by differential display reverse transcription PcR (DDRt-PcR) (1,2,7). this technique has been widely used, as it is a simple method which does not require previous genomic information about the species (8,10,12,14).…”