Root hairs, derived from trichoblasts, are critical for plant growth and environmental adaptation. Although environmental cues are known to influence root hair development, how endogenous timing systems such as the circadian clock integrate into the core transcriptional network governing root hair formation remains unclear. Here, we show that the circadian clock-associated protein PSEUDO-RESPONSE REGULATOR5 (PRR5) physically interacts with ROOT HAIR DEFECTIVE6 (RHD6) and RHD6 LIKE1 (RSL1), two basic helix-loop-helix transcription factors essential for root hair initiation. Genetic analyses suggest that PRR proteins contribute to root hair development under long-day conditions in Arabidopsis thaliana. Simultaneous disruption of PRR5, PRR7, and PRR9 results in defective root hairs, whereas PRR5 overexpression markedly increases root hair density and length. Transcriptomic and RT-qPCR analyses reveal that PRRs enhance the expression of RHD6, RSL1, and multiple downstream root hair-responsive genes, while modulating their temporal expression patterns. Furthermore, PRR5-mediated root hair promotion requires RHD6/RSL1, and PRR proteins enhance RHD6-dependent activation of the RSL4 promoter. PRRs also contribute to root hair development under phosphate-deficient and salt-stress conditions. Together, these findings establish a molecular framework in which PRR proteins regulate the RHD6/RSL network to coordinate root hair development and environmental responses.
Ning Bai, Yan Zhao, Tianmei Wang et al.· Plant Science· 0 citations
Drought stress severely restricts the growth and yield of woody nut crops. The xyloglucan endotransglucosylase/hydrolase (XTH) gene family participates in plant developmental and stress responses, yet its functions in pecan (Carya illinoinensis) under water limitation remain largely uncharacterized. Here, we performed a genome-wide identification of the XTH family in pecan, identifying 34 members distributed across four phylogenetic clades. Transcriptome-based expression analysis showed that several CiXTH genes responded to drought stress, among which CiXTH18 exhibited strong and sustained induction. To investigate its function, CiXTH18 was overexpressed in Arabidopsis thaliana. Under PEG-induced osmotic stress, CiXTH18-overexpressing lines exhibited significantly prolonged primary root lengths compared to wild-type plants. Furthermore, detached leaf assays revealed that transgenic plants had lower water loss rates under dehydration conditions. In addition, DAB staining indicated reduced H2O2 accumulation in CiXTH18-overexpressing plants under osmotic stress. Quantitative real-time PCR analysis revealed that the drought-responsive gene DREB2A and the ABA biosynthesis-related gene NCED3 were more strongly induced in transgenic lines than in wild-type plants after PEG treatment. Promoter activity assays confirmed that CiXTH18 was responsive to ABA treatment. Collectively, our findings indicate that heterologous expression of CiXTH18 is associated with improved performance of Arabidopsis under PEG-induced osmotic stress and support CiXTH18 as a promising candidate for further functional investigation.
