The accumulation of H 2 O 2 (oxidative burst) and the progress of pathogen development were studied in compatible and incompatible wheat-brown rust interactions. The accumulation of H 2 O 2 was detected in 98AE7% of guard cells with appressoria 8 h post inoculation (hpi). The reaction in both susceptible and resistant plants declined 2-3 days post inoculation (dpi). The second phase of the oxidative burst was observed in the mesophyll and ⁄ or epidermis. In susceptible plants it began 4-5 dpi and was detected only in the epidermis. In resistant plants the response was observed in the mesophyll. In moderately resistant plants it was induced 1-3 dpi, and the percentage of infection units reached 80-90% 8 dpi. This corresponded with severe necrotic symptoms. In highly resistant plants, the oxidative burst was short and transient. The percentage of infection units with H 2 O 2 accumulation reached its highest level (60-70%) 2 dpi, and decreased thereafter. Four days later, the low percentage and weak DAB staining indicated very low H 2 O 2 accumulation. The localization and the time-course changes of the oxidative burst correlated with the profiles of the micronecrotic response, haustorium mother cell formation and pathogen development termination. An early and localized induction of oxidative burst followed by its rapid quenching correlated with high resistance and almost no disease symptoms. The possible correlation of the oxidative burst and pathogen development patterns with the level and durability of resistance conferred by Lr genes are discussed.

Multigene families of CKX genes encode cytokinin oxidase/dehydrogenase proteins (CKX), which regulate cytokinin content in organs of developing plants. It has already been documented that some of them play important roles in plant productivity. The presented research is the first step of comprehensive characterization of the bread wheat TaCKX gene family with the goal to select genes determining yield-related traits. The specificity of expression patterns of fifteen formerly annotated members of the TaCKX family was tested in different organs during wheat development. Based on this, the genes were assigned to four groups: TaCKX10 , TaCKX5 and TaCKX4 , highly specific to leaves; TaCKX3 , TaCKX6 and TaCKX11 , expressed in various levels through all the organs tested; TaCKX1 , TaCKX2 . 3 , TaCKX2 . 2 , TaCKX2 . 1 , TaCKX2 . 4 and TaCKX2 . 5 specific to developing spikes and inflorescences; TaCKX9 , TaCKX8 and TaCKX7 , highly specific to roots. Amplification products of tested genes were mapped to the chromosomes of the A, B or D genome using T . aestivum Ensembl Plants. Based on analysis of TaCKX transcripts as well as encoded amino acids in T . aestivum and Hordeum vulgare the number of CKX genes in wheat was limited to 11 and new numbering of selected TaCKX genes was proposed. Moreover, we found that there were developmental differences in expression of TaCKX in the first and the second spike and expression of some of the genes was daily time dependent. A very high and significant correlation was found between expression levels of TaCKX7 and TaCKX9 , genes specific to seedling roots, TaCKX1 , TaCKX2 . 1 and TaCKX2 . 2 , specific to developing spikes, and the group of TaCKX3 , 4 , 5 , 6 , 10 and 11 , highly expressed in leaves and other organs. The genes also co-operated among organs and were included in two groups representing younger or maturating stages of developing plants. The first group was represented by seedling roots, leaves from 4-week old plants, inflorescences and 0 DAP spikes; the...

In wheat, adult plant resistance (APR) to leaf rust (Puccinia triticina), is effective in restricting pathogen growth and provides durable resistance against a wide range of virulent forms of P. triticina. Despite the importance, there is limited knowledge on the molecular basis of this type of resistance. We isolated and characterized the wall-associated kinase encoding gene in wheat, and assigned it as TaWAK6. Localization of TaWAK6 homeologs in A and B wheat subgenomes was consistent with the presence of the gene's orthologs in T. urartu (AA) and T. dicoccoides (AABB) and with the absence of its orthologs in Aegilops tauschii (DD). Overexpression of TaWAK6 did not change the wheat phenotype, nor did it affect seedling resistance. However, the adult plants overexpressing TaWAK6 showed that important parameters of APR were significantly elevated. Infection types scored on the first (flag), second and third leaves indicated elevated resistance, which significantly correlated with expression of TaWAK6. Analysis of plant-pathogen interactions showed a lower number of uredinia and higher rates of necrosis at the infection sites and this was associated with smaller size of uredinia and a longer latent period. The results indicated a role of TaWAK6 in quantitative partial resistance similar to APR in wheat. It is proposed that TaWAK6, which is a non-arginine-aspartate (non-RD) kinase, represents a novel class of quantitative immune receptors in monocots. OPEN ACCESSCitation: Dmochowska-Boguta M, Kloc Y, Zielezinski A, Werecki P, Nadolska-Orczyk A, Karlowski WM, et al. (2020) TaWAK6 encoding wall-associated kinase is involved in wheat resistance to leaf rust similar to adult plant resistance. PLoS ONE 15(1): e0227713. https://doi.

The goal of this work was to establish which enzymes -peroxidases or NADPH oxidases -play the most important role in the resistance-related oxidative burst response of wheat to infection by brown rust (Puccinia triticina). The expression of four peroxidases and two NADPH oxidases was analysed in the susceptible wheat cv. Thatcher and isogenic lines with different Lr resistance genes after pathogen inoculation. Of the peroxidases, TaPrx118 and TaPrx112 were induced several times more strongly than TaPrx103 and TaPrx107. The induction of peroxidases was more pronounced than that of NADPH oxidases. The patterns of peroxidase expression clearly differentiated moderately resistant from highly resistant lines and corresponded to oxidative response profiles. The possible involvement of peroxidases or NADPH oxidases was verified with enzyme-specific inhibitors. The oxidative burst in the susceptible cv. Thatcher and in the lines TcLr24, TcLr25, TcLr9 was peroxidase-dependent, while the response in line TcLr26 was NADPH-oxidase-dependent. It is postulated that class III peroxidases play a leading role in the formation of reactive oxygen species molecules during the response of wheat to pathogen infection. The results suggest a high level of redundancy of some peroxidase genes induced in biotic stress. The role of both enzyme systems in wheat response/resistance to brown rust is discussed in relation to the oxidative response, the efficiency of resistance, and the presence and origin of particular Lr resistance genes.

Benzoxazinoids (BXs) are secondary metabolites with diverse functions, but are primarily involved in protecting plants, mainly from the family Poaceae, against insects and fungal pathogens. Rye is a cereal crop that is highly resistant to biotic stresses. However, its susceptibility to brown rust caused by Puccinia recondita f. sp. secalis (Prs) is still a major problem affecting its commercial production. Additionally, the genetic and metabolic factors related to this disease remain poorly characterized. In this study, we investigated whether and to what extent the brown rust infection and the inoculation procedure affect the contents of specific BXs (HBOA, GDIBOA, DIBOA, GDIMBOA, DIMBOA, and MBOA) and the expression of genes related to BX (ScBx1-5, ScIgl, and Scglu). We revealed that treatments with water and a urediniospore suspension usually downregulate gene expression levels. Moreover, HBOA and DIBOA contents decreased, whereas the contents of the remaining metabolites increased. Specifically, the MBOA content increased more after the mock treatment than after the Prs treatment, whereas the increase in GDI-BOA and GDIMBOA levels was usually due to the Prs infection, especially at two of the most critical time-points, 17 and 24 h post-treatment. Therefore, GDIBOA and GDIMBOA are glucosides that are important components of rye defence responses to brown rust. Furthermore, along with MBOA, they protect rye against the stress associated with the inoculation procedure used in this study.