Water uptake by roots is essential for plant growth and stress acclimation. We previously showed that the XYLEM NAC DOMAIN 1 (XND1) transcription factor negatively regulates root hydraulic conductivity (Lpr) in Arabidopsis (Arabidopsis thaliana). Here, we show that XND1 physically interacts with the transcription factor DNA-binding with One Finger 4.6 (DOF4.6). Analyses of loss-of-function mutants and overexpression lines revealed that, similar to XND1, DOF4.6 negatively regulates Lpr. DOF4.6 and XND1 jointly modulate downstream gene expression, inhibiting root xylem formation. Notably, DOF4.6 facilitates XND1 binding to the promoter of XYLEM CYSTEINE PROTEASE 1, the product of which controls programmed cell death during xylem development. DOF4.6 also independently binds to the promoters of the aquaporins PIP2;5 and PIP2;6, thereby suppressing their expression and exerting potential direct regulatory effects on membrane water transport. Importantly, the dof4.6 loss-of-function alleles showed significantly enhanced resistance to drought stress. Collectively, our findings demonstrate that DOF4.6 plays a crucial role in root hydraulics and drought stress responses, partially in concert with XND1 and through combined effects on xylem formation and aquaporin functions.

Iron (Fe) is an essential mineral nutrient and a metal cofactor required for many proteins and enzymes involved in the processes of DNA synthesis, respiration, and photosynthesis. Iron limitation can have detrimental effects on plant growth and development. Such effects are mediated, at least in part, through the generation of reactive oxygen species (ROS). Thus, plants have evolved a complex regulatory network to respond to conditions of iron limitations. However, the mechanisms that couple iron deficiency and oxidative stress responses are not fully understood. Here, we report the discovery that an Arabidopsis thaliana monothiol glutaredoxin S17 (AtGRXS17) plays a critical role in the plants ability to respond to iron deficiency stress and maintain redox homeostasis. In a yeast expression assay, AtGRXS17 was able to suppress the iron accumulation in yeast ScGrx3/ScGrx4 mutant cells. Genetic analysis indicated that plants with reduced AtGRXS17 expression were hypersensitive to iron deficiency and showed increased iron concentrations in mature seeds. Disruption of AtGRXS17 caused plant sensitivity to exogenous oxidants and increased ROS production under iron deficiency. Addition of reduced glutathione rescued the growth and alleviates the sensitivity of atgrxs17 mutants to iron deficiency. These findings suggest AtGRXS17 helps integrate redox homeostasis and iron deficiency responses.

With global climate change ongoing, the frequency and intensity of extreme weather events have increased annually. Hulless barley (Hordeum vulgare L. var. nudum), a primary crop cultivated in the Qinghai–Tibet Plateau mountains, frequently encounters multiple abiotic stresses including low temperature, high salinity, and drought. Among these stresses, drought has emerged as a critical environmental constraint affecting sustainable agricultural development worldwide. Establishing a drought resistance evaluation system for the hulless barley germplasm during its seedling stages could provide a theoretical foundation for screening and breeding drought-tolerant cultivars to address climate change challenges. This study employed two drought-sensitive (YC85 and YC88) and two drought-tolerant (ZY1252 and ZY1100) cultivars to develop an effective drought resistance evaluation protocol for hulless barley. Our findings identified several reliable indicators for assessing drought tolerance at the seedling stage: fresh mass, chlorophyll fluorescence parameters (F_v/F_m, NPQ, and R_FD), photosynthetic parameters (E and gsw), and reactive oxygen species (ROS) levels. The established evaluation system was subsequently applied to three uncharacterized cultivars (ZY673, ZY1403, and KL14). The results classified all three as drought-sensitive, with ZY1403 exhibiting the highest sensitivity. Our work has established a comprehensive drought resistance evaluation framework for Tibetan hulless barley. Furthermore, this study provides valuable insights for optimizing cultivation practices and water resource management strategies, offering theoretical guidance for agricultural adaptation to climate change.

Soil salinization has emerged as a significant challenge for crop production worldwide. Xylem adjustments through plastic development and sodium unloading from root xylem, as mediated by sodium transporter HKT1, both play crucial roles in controlling sodium transport and salt tolerance in plants. Here, we report that XYLEM NAC DOMAIN 1 (XND1) of Arabidopsis contributes to the coordination of these two processes during salt stress responses. XND1 is predominantly accumulated in roots under salt exposure and confers plant salt tolerance, as demonstrated by analysis of overexpression and loss-of-function mutant lines. XND1 mediates discontinuous root protoxylem differentiation under salt stress, potentially limiting sodium transport. In addition, XND1 directly targets and activates the expression of HKT1 , thereby facilitating the removal of sodium from root xylem. We also show that MYBS2, a MYB transcription factor, interacts with XND1 to antagonistically regulate HKT1 , whereas VND-INTERACTING 2 (VNI2), a NAC transcription factor, activates XND1 in response to salt stress. Characterization of the XND1 ortholog of rice suggests a conserved regulatory role under salt stress. Collectively, our findings unveil an XND1-centered regulatory network that modulates salt stress response, through the integration of root xylem developmental plasticity and sodium unloading.