Related Experiment Video
Updated: Mar 3, 2026
Investigating Interactions Between Histone Modifying Enzymes and Transcription Factors in vivo by Fluorescence Resonance Energy Transfer
Published on: October 14, 2022
Functional characterization of cucumber (Cucumis sativus L.) Clade V MLO genes
Jeroen A Berg1, Michela Appiano1, Gerard Bijsterbosch1
1Plant Breeding, Wageningen University & Research, Droevendaalsesteeg 1, 6708 PB, Wageningen, The Netherlands.
Background:
Powdery mildew (PM) causing fungi are well-known pathogens, infecting over 10.000 plant species, including the economically important crop cucumber (Cucumis sativus L.). Loss-of-function mutations in clade V MLO genes have previously been shown to lead to recessively inherited broad-spectrum resistance to PM in several species. In cucumber, one clade V MLO homolog (CsaMLO8) was previously identified as being a susceptibility factor to PM. Two other closely related homologs (CsaMLO1 and CsaMLO11) were found, but their function was not yet unravelled.
Methods:
CsaMLO1 and CsaMLO11 were cloned from cucumber and overexpressed in a tomato mlo mutant. The transcript abundances of all three CsaMLO genes in different cucumber tissues were quantified using qRT-PCR and RNA-seq, with and without inoculation with the cucumber PM fungus Podosphaera xanthii. Allelic variation of CsaMLO1 and CsaMLO11 was screened in silico in sequenced cucumber germplasm.
Results:
Heterologous overexpression of all three CsaMLO genes in the tomato mlo mutant restored susceptibility to PM caused by Oidium neolycopersici, albeit to a different extent: whereas overexpression of CsaMLO1 or CsaMLO8 completely restored susceptibility, overexpression of CsaMLO11 was only partially able to restore PM susceptibility. Furthermore, it was observed by qRT-PCR and RNA-seq that CsaMLO8 was significantly higher expressed in non-inoculated cucumber compared to the other two MLO genes. However, inoculation with P. xanthii led to upregulation of CsaMLO1, but not to upregulation of CsaMLO8 or CsaMLO11.
Conclusions:
Both CsaMLO1 and CsaMLO11 are functional susceptibility genes, although we conclude that based on the transcript abundance CsaMLO8 is probably the major clade V MLO gene in cucumber regarding providing susceptibility to PM. Potential loss-of-function mutations in CsaMLO1 and CsaMLO11 have not been identified. The generation and analysis of such mutants are interesting subjects for further investigation.
Insights
Cucumber powdery mildew (PM) resistance can be enhanced by targeting MLO genes. This study identifies CsaMLO1 and CsaMLO11 as susceptibility genes, with CsaMLO8 being the primary factor for PM susceptibility in cucumber.
Area of Science:
- Plant pathology
- Molecular genetics
- Crop science
Background:
- Powdery mildew (PM) is a significant fungal disease affecting numerous plant species, including cucumber (Cucumis sativus L.).
- Loss-of-function mutations in clade V MLO genes confer broad-spectrum resistance to PM in various plants.
- In cucumber, CsaMLO8 is a known PM susceptibility factor, while the roles of CsaMLO1 and CsaMLO11 were previously unknown.
Purpose of the Study:
- To investigate the function of CsaMLO1 and CsaMLO11 in cucumber powdery mildew susceptibility.
- To compare the roles of CsaMLO1, CsaMLO8, and CsaMLO11 in PM susceptibility.
Main Methods:
- Cloning and heterologous overexpression of CsaMLO1 and CsaMLO11 in a tomato mlo mutant.
- Quantification of CsaMLO gene transcript levels using qRT-PCR and RNA-seq in cucumber tissues, with and without PM inoculation.
- In silico screening for allelic variation in CsaMLO1 and CsaMLO11.
Main Results:
- Heterologous expression of CsaMLO1, CsaMLO8, and CsaMLO11 restored PM susceptibility in the tomato mlo mutant, with CsaMLO1 and CsaMLO8 showing complete restoration and CsaMLO11 showing partial restoration.
- CsaMLO8 exhibited higher basal expression in cucumber tissues compared to CsaMLO1 and CsaMLO11.
- PM inoculation led to the upregulation of CsaMLO1, but not CsaMLO8 or CsaMLO11.
Conclusions:
- CsaMLO1 and CsaMLO11 function as susceptibility genes in cucumber PM.
- CsaMLO8 is likely the predominant clade V MLO gene contributing to PM susceptibility in cucumber, based on expression levels.
- Further research into potential loss-of-function mutations in CsaMLO1 and CsaMLO11 is warranted.
Related Concept Videos
02:02Cis-regulatory Sequences
01:20Mismatch Repair
The Mutator Protein Family Plays a Key Role in DNA Mismatch Repair
The human genome has more than 3 billion base pairs of DNA per cell. Prior to cell division, that vast amount of genetic...
01:36Mismatch Repair
01:29Modern Molecular Taxonomy