Valarik, M. | Search bioRxiv

bioRxiv2026

Insight into GABA shunt-associated aldehyde dehydrogenases (ALDH) and stress responses of ALDH superfamily in moss and barley

We explored the expression of the aldehyde dehydrogenase (ALDH) superfamily in two model plants, Physcomitrium patens (moss) and Hordeum vulgare (barley), under various stress conditions. The ALDH enzymes are crucial for oxidizing aldehydes to carboxylic acids and are involved in multiple metabolic pathways. We found significant differences in enzyme expression between moss and barley within the same ALDH families. We then focused on the ALDH5, ALDH10, and ALDH21 families, which are part of the {gamma}-aminobutyric acid (GABA) shunt, noting that the ALDH21 family is absent in barley. The kinetic properties of ALDH10 and ALDH5 enzymes were analyzed, revealing that PpALDH5F1 exhibits high specificity for succinic semialdehyde (SSAL), a product of GABA. The crystal structure of PpALDH5F1 identified key residues for SSAL binding. Knockout mutants of moss aldh5F2, aldh10A1, and aldh21A1 showed slightly smaller colonies than the wild-type. GABA and glutamate levels were elevated in aldh5F2 and aldh21A1 knockouts due to a partially blocked GABA shunt pathway, while aldh10A1 knockout showed no changes in GABA levels. Transcriptomic data revealed a link between several genes, including six upregulated glutathione-S-transferase genes in all three aldh knockouts, suggesting a direct compensatory mechanism for oxidative stress protection via conjugation of undegraded aldehydes to glutathione. HighlightMoss knockouts of GABA shunt-associated aldehyde dehydrogenases display slower growth, changes in levels of glutamate, glutamine and GABA, and result in upregulation of several unique glutathione-S-transferase genes.

plant biology↗

bioRxiv2017

Association mapping and haplotype analysis of the pre-harvest sprouting resistance locus Phs-A1 reveals a causal role of TaMKK3-A in global germplasm

Pre-harvest sprouting (PHS) is an important cause of quality loss in many cereal crops and is particularly prevalent and damaging in wheat. Resistance to PHS is therefore a valuable target trait in many breeding programmes. The Phs-A1 locus on wheat chromosome arm 4AL has been consistently shown to account for a significant proportion of natural variation to PHS in diverse mapping populations. However the deployment of sprouting resistance is confounded by the fact that different candidate genes, including the tandem duplicated Plasma Membrane 19 (PM19) genes and the mitogen-activated protein kinase kinase 3 (TaMKK3-A) gene, have been proposed to underlie Phs-A1. To further define the Phs-A1 locus, we constructed a physical map across this interval in hexaploid and tetraploid wheat. We established close proximity of the proposed candidate genes which are located within a 1.2 Mb interval. An association analysis of diverse germplasm used in previous genetic mapping studies suggests that TaMKK3-A, and not PM19, is the major gene underlying the Phs-A1 effect in European, North American, Australian and Asian germplasm. We identified the non-dormant TaMKK3-A allele at low frequencies within the A-genome diploid progenitor Triticum urartu genepool, and show an increase in the allele frequency in modern varieties. In UK varieties, the frequency of the dormant TaMKK3-A allele was significantly higher in bread-making quality varieties compared to feed and biscuit-making cultivars. Analysis of exome capture data from 58 diverse hexaploid wheat accessions identified fourteen haplotypes across the extended Phs-A1 locus and four haplotypes for TaMKK3-A. Analysis of these haplotypes in a collection of UK and Australian cultivars revealed distinct major dormant and non-dormant Phs-A1 haplotypes in each country, which were either rare or absent in the opposing germplasm set. The diagnostic markers and haplotype information reported in the study will help inform the choice of germplasm and breeding strategies for the deployment of Phs-A1 resistance into breeding germplasm.

plant biology↗