Effect of developmental dynamics on WRKY expression in barley with varying phenologies and trichome micromorphologies

Background barley landraces from regions with challenging climates near the origin of crop domestication present valuable drought tolerance traits. With global warming, water scarcity is expected to become more frequent and severe, threatening food security. Moreover, abiotic stresses such as drought often coincide with pathogen infections, compounding their negative effects on plants. Certain transcription factors—such as WRKYs—play key regulatory roles in plant responses to abiotic stresses, including drought. This raises the following question: how do differences in trichome micromorphology and the expression of selected WRKY transcription factors influence barley resistance to drought and pathogen infection under multifactorial stress conditions? Results various barley genotypes were assessed for differences in traits such as trichome density and micromorphology under multifactorial stress conditions. In addition, three distinct WRKY transcription factors (TFs) were examined for their roles in plant stress responses. The expression of these genes responded differently to stress intensity: the expression of WRKY51 and WRKY70 significantly changed, whereas that of WRKY34 was more closely linked to plant development. Drought also negatively impacted photosynthetic efficiency, with moderate drought causing only minor changes in chlorophyll a fluorescence kinetics. Conclusions although no significant differences in Fusarium resistance were detected among the genotypes, two late-heading genotypes (LubBW1 and LubWa1, late-heading, a glossy line derived from a cross between Lubuski × BW408 and late-heading, a glaucous line derived from a cross between Lubuski × Wa1, respectively) presented contrasting trichome structures, with LubBW1 potentially trapping pathogen conidia. Another genotype, CamBW1 (early-heading, a glossy line derived from a cross between CamB × BW408), showed early drought effects on fluorescence parameters but may have activated resistance mechanisms at flowering. This study supports the concept of flowering-induced resistance in barley.