Missense mutation of a class B heat shock factor is responsible for the tomato bushy root-2 phenotype

Zoltan Kevei; Silva Demetryus Silva Ferreira; Cristina Maria Perez Casenave; Tomasz Kurowski; Fady Mohareb; Daniel Rickett; Chris Stain; Andrew J Thompson

doi:10.1186/s43897-022-00025-0

Missense mutation of a class B heat shock factor is responsible for the tomato bushy root-2 phenotype

Mol Hortic. 2022 Feb 8;2(1):4. doi: 10.1186/s43897-022-00025-0.

Authors

Zoltan Kevei¹, Silva Demetryus Silva Ferreira², Cristina Maria Perez Casenave², Tomasz Kurowski², Fady Mohareb², Daniel Rickett³, Chris Stain³, Andrew J Thompson²

Affiliations

¹ Cranfield Soil and AgriFood Institute, College Road, Cranfield University, Bedfordshire, MK43 0AL, UK. z.l.kevei@cranfield.ac.uk.
² Cranfield Soil and AgriFood Institute, College Road, Cranfield University, Bedfordshire, MK43 0AL, UK.
³ Syngenta Crop Protection, Jealott's Hill International Research Centre, Bracknell, Berkshire, RG42 6EY, UK.

Abstract

The bushy root-2 (brt-2) tomato mutant has twisting roots, and slower plant development. Here we used whole genome resequencing and genetic mapping to show that brt-2 is caused by a serine to cysteine (S75C) substitution in the DNA binding domain (DBD) of a heat shock factor class B (HsfB) encoded by SolycHsfB4a. This gene is orthologous to the Arabidopsis SCHIZORIZA gene, also known as AtHsfB4. The brt-2 phenotype is very similar to Arabidopsis lines in which the function of AtHsfB4 is altered: a proliferation of lateral root cap and root meristematic tissues, and a tendency for lateral root cap cells to easily separate. The brt-2 S75C mutation is unusual because all other reported amino acid substitutions in the highly conserved DBD of eukaryotic heat shock factors are dominant negative mutations, but brt-2 is recessive. We further show through reciprocal grafting that brt-2 exerts its effects predominantly through the root genotype even through BRT-2 is expressed at similar levels in both root and shoot meristems. Since AtHsfB4 is induced by root knot nematodes (RKN), and loss-of-function mutants of this gene are resistant to RKNs, BRT-2 could be a target gene for RKN resistance, an important trait in tomato rootstock breeding.Gene & accession numbersSolycHsfB4a - Solyc04g078770.

Keywords: Bushy root-2; Genetic mapping; HsfB4; Root knot nematode resistance; SCHIZORIZA; Tomato.

Abstract

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