Cadmium (Cd) is an environmental pollutant that potentially threatens human health worldwide. Developing approaches for efficiently treating environmental Cd is a priority. Selenium (Se) plays important role in the protection of plants against various abiotic stresses, including heavy metals. Previous research has shown that Se can alleviate Cd toxicity, but the molecular mechanism is still not clear. In this study, we explore the function of auxin and phosphate (P) in tobacco (Nicotiana tabacum), with particular focus on their interaction with Se and Cd. Under Cd stress conditions, low Se (10 μM) significantly increased the biomass and antioxidant capacity of tobacco plants and reduced uptake of Cd. We also measured the auxin concentration and expression of auxin-relative genes in tobacco and found that plants treated with low Se (10 μM) had higher auxin concentrations at different Cd supply levels (0 μM, 20 μM, 50 μM) compared with no Se treatment, probably due to increased expression of auxin synthesis genes and auxin efflux carriers. Overexpression of a high affinity phosphate transporter NtPT2 enhanced the tolerance of tobacco to Cd stress, possibly by increasing the total P and Se content and decreasing Cd accumulation compared to that in the wild type (WT). Our results show that there is an interactive mechanism among P, Se, Cd, and auxin that affects plant growth and may provide a new approach for relieving Cd toxicity in plants.

Maize, one of the world’s major food crops, is facing the challenge of rising temperature. Leaf senescence is the most significant phenotypic change of maize under heat stress at the seedling stage, but the underlying molecular mechanism is still unknown. Here, we screened for three inbred lines (PH4CV, B73, and SH19B) that showed differentially senescing phenotypes under heat stress. Among them, PH4CV showed no obviously senescing phenotype under heat stress, while SH19B demonstrated a severely senescing phenotype, with B73 being between the two extremes. Subsequently, transcriptome sequencing showed that differentially expressed genes (DEGs) were generally enriched in response to heat stress, reactive oxygen species (ROS), and photosynthesis in the three inbred lines under heat treatment. Notably, ATP synthesis and oxidative phosphorylation pathway genes were only significantly enriched in SH19B. Then, the expression differences of oxidative phosphorylation pathways, antioxidant enzymes, and senescence-related genes in response to heat stress were analyzed in the three inbred lines. In addition, we demonstrated that silencing ZmbHLH51 by virus-induced gene silencing (VIGS) inhibits the heat-stress-induced senescence of maize leaves. This study helps to further elucidate the molecular mechanisms of heat-stress-induced leaf senescence at the seedling stage of maize.

Non-heading Chinese cabbage (NHCC) is a highly economically valuable leafy vegetable widely grown in Asian regions. However, it undergoes rapid leaf yellowing and wilting during postharvest storage, which subsequently cause rapid quality decline and loss of nutritional components. Abscisic acid (ABA) promotes postharvest leaf senescence, while hydrogen-rich water (HRW) is widely used in postharvest preservation due to its excellent antioxidant properties; yet, the mechanism through which they interact to regulate postharvest senescence in NHCC remains unclear. Herein we found that exogenous HRW effectively delayed dark- and ABA-induced postharvest leaf senescence in NHCC, significantly maintained chlorophyll content, inhibited oxidative damage, and preserve nutritional components such as soluble sugars and vitamin C. The underlying mechanism was HRW inhibiting chlorophyll degradation by repressing the expression of chlorophyll catabolic genes like NYC1, NYE1, and PPH1. Meanwhile, HRW effectively lowered the accumulation of MDA and H₂O₂, elevated both the enzymatic activities and transcript abundance of SOD and CAT, and downregulated the transcript levels of RbohB, RbohC, RbohD, and RbohE, thereby maintaining reactive oxygen species (ROS) homeostasis. In addition, HRW negatively regulated ABA biosynthesis by inhibiting the transcript levels of ABA1, ABA2 and ABA3, while promoting the transcription of CYP707A1, CYP707A2 and CYP707A3. It also dampened the transcript abundance of ABA signaling components including PYL5, ABI1, and ABF3, thus blocking ABA signal transduction and alleviating its senescence-promoting effect. Collectively, this study confirms that HRW mitigates leaf senescence induced under dark and ABA conditions in NHCC via multiple synergistic pathways.