Thidiazuron (TDZ) is a synthetic growth regulator with cytokinin-like activity, widely used in biotechnology, but its physiological effects during the early stages of plant development are not yet fully understood. In this study, the impact of increasing concentrations of TDZ on the germination and early development of Arabidopsis thaliana was evaluated, with particular attention to physiological responses and their dose-dependent patterns. Seeds of the Col-0 ecotype were germinated in the presence of TDZ and analyzed using integrated approaches including morphological observations, photosynthetic efficiency measurements, and metabolic and hormonal profile analysis. The results show that low concentrations of TDZ do not significantly alter the main physiological parameters, while higher doses induce progressive alterations in cotyledon vascular pattern, hormonal imbalances, and a reduction in photosynthetic efficiency, indicating a functional impairment. Transcriptomic analysis revealed coordinated modulation of genes involved in hormonal regulation, energy metabolism, and stress responses, consistent with the observed phenotypes. Overall, the study demonstrates that TDZ exerts distinct and highly dose-dependent physiological effects, delineating a continuum ranging from responses compatible with normal development to those indicative of impaired development to conditions of physiological stress, and providing useful insights for a critical assessment of the benefits and risks associated with the use of this compound.
Eva Campo, F. de Marchi, Giulia Giovanna Salerno et al.· Plant physiology and biochem...· 0 citations
Heat stress is one of the most damaging abiotic constraints on crop productivity, and its consequences are expected to intensify as extreme temperature events become more frequent and severe. Pepper (Capsicum annuum L.) is particularly vulnerable to sustained high temperatures, which can disrupt photosynthetic performance, cellular homeostasis, and redox regulation. However, the physiological and transcriptional dynamics underlying genotype-dependent responses to prolonged heat exposure remain insufficiently understood. We combined repeated physiological measurements with time-course RNA sequencing to compare GPC003240, previously identified as a candidate heat-tolerant accession, with two non-elite accessions, GPC010350 and GPC014930, which are phenotypically divergent from each other, under 40/30 °C Day/night temperatures for up to six days. GPC010350 maintained comparatively stable photosystem II performance and higher stomatal conductance, whereas GPC014930 showed progressive photochemical impairment and lower conductance; GPC003240 displayed a distinct, moderately responsive profile. Transcriptomic responses showed partial functional convergence during the early phase of stress exposure but diverged markedly after six days. When gene expression at day 6 was compared with the pre-treatment baseline separately within each genotype, 4,436 differentially expressed genes were detected in GPC010350, compared with 680 in GPC003240 and only 78 in GPC014930. The late response of GPC010350 was associated with enrichment of RNA- and ribosome-related, biosynthetic, DNA-repair, and genome-maintenance functions. By contrast, GPC014930 showed negative enrichment of photosynthesis, plastid organization, redox homeostasis, and translation-related processes. Global co-expression analysis identified a time-decreasing photosynthesis-associated module (ME5) and two time-increasing modules, ME12 and ME19, that were enriched in genes contributing to the late GPC010350 response. Integration of differential expressions, module membership, and functional annotation highlighted a heat shock transcription factor (Caz03g27980), HSP101 (Caz03g07770), and a dual-specificity phosphatase (Caz05g20970) as candidates for further investigation. Overall, the results suggest that genotype-dependent responses to prolonged heat exposure were associated not only with the magnitude of early transcriptional change, but also with differences in the temporal organization of stress-response, maintenance, and metabolic processes. The contrasting responses of the non-elite accessions GPC010350 and GPC014930 further highlight the value of phenotypically diverse germplasm for uncovering mechanisms relevant to future heat-tolerance breeding.
M. Martina, E. Vergnano, F. Secchi et al.· bioRxiv· 0 citations
