Molecular and histochemical characterisation of two distinct poplar Melampsora leaf rust pathosystems

Abstract

In this study, we compared interactions of two Melampsora foliar rust species with poplar, which resulted in either limited or abundant pathogen proliferation. In the pathosystem exhibiting limited pathogen growth, a defence response was observed after invasion of poplar leaf tissues by the biotroph, with late and clear production of reactive oxygen species (ROS) and other products. Characterisation of the histological, biochemical and transcriptional events occurring in both pathosystems showed striking similarity with components of plant defence reactions observed during qualitative resistance. Key components associated with development of an active defence response, such as up-regulation of pathogenesis-related (PR) genes, were observed during infection. Moreover, the time course and strength of gene induction appear to be critical determinants for the outcome of the tree-pathogen interaction. This work provides basic biochemical characterisation and expression data for the study of so-called partial resistance in the poplar-rust pathosystem, which is also applicable to other plant-pathogen interactions resulting in quantitative disease resistance.

Apoplast proteome reveals that extracellular matrix contributes to multistress response in poplar

“…Leaves LPI 8 and LPI 9 (leaf plastochron index, [132]) were used for all experiments from 1 m tall poplar trees (16 fully expanded leaves). Inoculation of leaf discs with Melampsora was conducted as previously described [133]. Briefly, disks of 2 cm in diameter were inoculated on the abaxial side with M. medusae f. sp.…”

The Poplar-Poplar Rust Interaction: Insights from Genomics and Transcriptomics

“…Transcripts induced in LCM-isolated uredinia are more diverse and include several cell-cycle- and cell-rescue-related transcripts [9]. The induction of cell cycle transcripts is supportive of the intense cell division activity observed in the microdissected sporulation area, while cell-rescue- and defense-related transcripts might reflect an active defense from the rust fungus in response to the late activation of poplar reactions such as oxidative burst or expression of defense genes reported in compatible poplar-poplar rust interactions [5, 8] (Figure 3). Interestingly, transcripts accumulated in the sporulation area were predominantly detected in resting urediniospores and at 168 hpi in the time-course expression study [52].…”

“…Cytological observations revealed a highly localized hypersensitive response (HR), with collapsed infected plant cells and accumulation of monolignols around infection sites after 48 hpi in the incompatible interaction [6, 7]. At later time points in the compatible interaction, anthocyanidins, lignin, pectin, and hydrogen peroxide accumulate around infection sites and likely participate in late defense responses and partial resistance in poplar [5, 8, 11]. …”

“…Transcriptome studies conducted on poplar-poplar rust interactions revealed the early induction of defense responses during the incompatible interaction, referred to as complete or host-specific resistance, whereas a late induction of defense responses was observed in the case of compatible interactions and partial resistance [7, 8, 11, 49, 50] (Figure 3). These studies indicate that defense reactions are governed by common molecular bases in both perennial and annual species.…”

The genomics of poplar-rust interactions to improve tree resistance against fungal disease

“…Similarly we have also shown that mitogen activated protein kinases (MAPKs) are associated with poplar disease resistance against Melampsora rust [2]. New data obtained from various experimental approaches have directed our focus on two important families of transcription factors; the jasmonate ZIM-domain (JAZ) and Cys2/His2 zinc-finger protein (ZFP) families.…”