PMID: 1423716 A single amino-acid change in the iron-sulphur protein subunit of succinate dehydrogenase confers resistance to carboxin in Ustilago maydis

[MPiovesana]

Curated by @MPiovesana
https://canto.phi-base.org/curs/534af7fad99f50d0

[MPiovesana]

Short paper where authors identify mutations in the SDH2 gene (Ip subunit of succinate dehydrogenase) of carboxin-resistant and -sensitive strains of Ustilago maydis. By comparing the Ip alleles, authors identify a single amino acid substitution between the two, which is the presence of a histidine at position 253* of the Cbx-sensitive allele, and a leucine at the same position in the Cbx-resistant allele. Authors generated the Ip-Leu253 allele by site-directed mutagenesis of the Cbx-sensitive allele, which was transformed into the sensitive strain. Cbx-resistant transformants were identified, confirming that the His253Leu substitution confers resistance to this fungicide.

NOTE: typo in figure 3 identifies the His/Leu residue position as 257, when the correct numbering is 253. The correct information is found at the text (last paragraph), which agrees with the numbering of the protein sequence deposited on Uniprot.

[MPiovesana]

Uniprot ID: by searching SDH2 Ustilago maydis on Uniprot, a single entry is retrieved (P32420); the protein sequence associated with this entry corresponds with the one shown in the article.

[MPiovesana]

Strain: Cbx-sensitive strain IMI103761 was used as recipient for genetic transformation.

[MPiovesana]

Genotype creation: the SDH2 (Ip) allele from the recipient strain was used as template for the introduction of the mutation leading to the His253Leu substitution, and therefore, an allele type amino acid substitution was chosen when creating this genotype. Expression levels were not tested, but from the text we can infer that the mutant allele was introduced to be randomly integrated into the genome (no mention of homologous recombination/gene replacement); for this reason, Ectopic was selected. Endogenous SDH2 present was added to background.

[MPiovesana]

Genotype annotation: single annotation with PHIPO term "resistance to carboxin". Generation of carboxin-resistant transformants is only mentioned in the text (no figures/tables).

[MPiovesana]

Curation completed pending review.

[CuzickA]

Single annotation looks fine

Next steps

1. add new strain to strain list DONE 13_02_2024 ab13338
2. try to add AE alteration in archetype DONE 13_02_2024

[CuzickA]

AE alteration in archetype

SDH2(aaH253L)[Ectopic] 'H277L; Sdh2 (SdhB); PYRNTE'

Issue with residue position, authors state 257 and 253 as noted above by Maiara. The correct numbering is 253. (see below for my FRAST alignments)

It looks at though both Nichola and the Mair et al group have used the incorrect residue position 257.

Nichola's table

Mair et al 2016

Used FASTA AA sequence for reviewed https://www.uniprot.org/uniprotkb/P32420/entry
(Note Sdh2 = SdhB)

This looks correct.
There may have been an error in Nicola and Mair tables.

[CuzickA]

Next steps

1. check AE alteration in archetype with Nichola.

Then session will be ready for approval.