Fusarium oxysporum f. sp. radicis-lycopersici (Forl) is a destructive soil-borne phytopathogenic fungus that causes Fusarium crown and root rot (FCRR) of tomato, leading to considerable field yield losses. In this study, we explored the antifungal capability of linalool, a natural plant volatile organic component, against Forl and its role in controlling FCRR symptoms in tomatoes. Our results showed that Forl mycelial growth was inhibited by the linalool treatment and that the linalool treatment damaged cell membrane integrity, enhanced reactive oxygen species levels, depleted glutathione, and reduced the activities of many antioxidant enzymes in Forl. Transcriptomic and proteomic analyses demonstrated that linalool also downregulated metabolic biosynthetic pathways at the transcript and protein levels, including redox, transporter activity, and carbohydrate metabolism in Forl. Moreover, linalool significantly decreased the expression of many Forl pathogenic genes, such as cell wall degrading enzymes (CWDEs) and G proteins, which is likely how a Forl infection was prevented. Importantly, exogenously applied linalool activated the salicylic acid (SA) and jasmonic acid (JA) defensive pathways to improve disease resistance and relieved the negative effects of Forl on plant growth. Taken together, we report that linalool is an effective fungicide against Forl and will be a promising green chemical agent for controlling FCRR.

Due to climate change, drought has become a major threat to rice (Oryza sativa L.) growth and yield worldwide. Understanding the genetic basis of drought tolerance in rice is therefore of great importance. Here, we identified a microRNA, miR1432, which regulates rice drought tolerance by targeting the CALMODULIN-LIKE2 (OsCaML2) gene. Mutation of MIR1432 (Bhardwaj et al., 2014). Moreover, recent studies have demonstrated that some miRNAs, such as miR164 (Fang et al., 2014), miR166 (Zhang et al., 2018), miR319 (Zhou et al., 2013) and miR408 (Hang et al., 2021), play important roles in regulating plant drought resistance. An improved understanding of the miRNA-mediated regulatory mechanisms involved in drought resistance would help to elucidate the regulatory networks that control drought stress responses and adaptation to water deficiency and may facilitate the genetic engineering of drought-tolerant crop varieties.

The macronutrient phosphorus is essential for plant growth and development. Plants have evolved multiple strategies to increase the efficiency of phosphate (Pi) acquisition to protect themselves from Pi starvation. However, the crosstalk between Pi homeostasis and plant development remains to be explored. Here, we report that overexpressing microRNA399 (miR399) in maize (Zea mays) is associated with premature senescence after pollination. Knockout of ZmPHO2 (Phosphate 2), a miR399 target, resulted in a similar premature senescence phenotype. Strikingly, we discovered that INDETERMINATE1 (ID1), a floral transition regulator, inhibits the transcription of ZmMIR399 genes by directly binding to their promoters, alleviating the repression of ZmPHO2 by miR399 and ultimately contributing to the maintenance of Pi homeostasis in maize. Unlike ZmMIR399 genes, whose expression is induced by Pi deficiency, ID1 expression was independent of the external inorganic orthophosphate status, indicating that ID1 is an autonomous regulator of Pi homeostasis. Furthermore, we show that ZmPHO2 was under selection during maize domestication and cultivation, resulting in a more sensitive response to Pi starvation in temperate maize than in tropical maize. Our study reveals a direct functional link between Pi-deprivation sensing by the miR399-ZmPHO2 regulatory module and plant developmental regulation by ID1.

Gray mold is a disease that often occurs in postharvest tomato fruits, leading to a significant decline in the fruits’ quality. In production, pesticides are mostly used to control gray mold, which negatively affect both the environment and food safety. The purpose of this article is to study the effects of linalool fumigation on controlling gray mold in tomato fruits and to further investigate the mechanism of linalool function, so as to provide technical support and a theoretical basis for the application of linalool in the green control of tomato gray mold. The results of the in vitro experiments showed that linalool fumigation had a strong inhibitory effect on the mycelial growth of Botrytis cinerea and that the fumigation of linalool inhibited the expansion of pathogens on tomato fruits. The disease index of tomato fruits in the linalool treatment was always lower than that of the control within 72 h after inoculation with Botrytis cinerea; at the end of experiment, the disease index of the control reached 100.0, which was only 8.0 with the 30 μL/L linalool treatment. Linalool fumigation increased the antioxidant capacity of the tomato fruits under Botrytis cinerea infection through regulating activities of SOD, POD and CAT as well as the ascorbic acid (AsA) content, which could be responsible for the lower malondialdehyde (MDA) accumulation. Linalool fumigation increased the activities of polyphenol oxidase (PPO), and phenylalanine ammonia-lyase (PAL) in tomato fruits, indicating that secondary metabolism was involved in the function of linalool in the regulation of tomato fruit resistance to pathogens. As the main enzymes related to cell structure, polygalacturonase (PG), cellulase (CL) and β-galactosidase (β-GAL) were inhibited by linalool, which could protect cell wall structures from damage, and strengthened the mechanical barrier against pathogen access to fruit flesh.

Melatonin (MT) is a phytohormone-like substance and is profoundly involved in modulating nearly all aspects of plant development and acclimation to environmental stressors. However, there remain no studies about the effects of MT on tomato seed germination under salt stress. Here we reported that the overexpression of caffeic acid O-methyltransferase 1 (SlCOMT1) significantly increased both MT content and salt tolerance in the germinated seeds of a transgenic tomato relative to wild type (WT) samples. Physiological investigation showed higher amylase activity in the stressed overexpression seeds than WT, leading to the promoted starch decomposition and enhanced soluble sugar content. The stimulated production of osmolytes and enhanced activities of SOD, POD, and CAT, together with the significant reduction in H₂O₂ and O₂^·− accumulation, were revealed in the stressed overexpression seeds relative to WT, largely accounting for their lower membrane lipid peroxidation. qPCR assay showed that, upon salt stress, the transcript abundance of hub genes related to germination (SlCYP707A1, SlABA1, SlGA3ox2 and SlGA2ox4) and stress tolerance (SlCDPK1, SlWRKY33 and SlMAPK1) were distinctly altered in the overexpression samples when compared to WT, providing a molecular basis for MT-mediated improvement of seed salt tolerance. Altogether, our observations shed new insights into biological functions of SlCOMT1 and could expand its utilization in genetic improvement of tomato salt tolerance in future.