Nitrogen (N) is a vital mineral component that can restrict the growth and development of plants if supplied inappropriately. In order to benefit their growth and development, plants have complex physiological and structural responses to changes in their nitrogen supply. As higher plants have multiple organs with varying functions and nutritional requirements, they coordinate their responses at the whole-plant level based on local and long-distance signaling pathways. It has been suggested that phytohormones are signaling substances in such pathways. The nitrogen signaling pathway is closely associated with phytohormones such as auxin (AUX), abscisic acid (ABA), cytokinins (CKs), ethylene (ETH), brassinosteroid (BR), strigolactones (SLs), jasmonic acid (JA), and salicylic acid (SA). Recent research has shed light on how nitrogen and phytohormones interact to modulate physiology and morphology. This review provides a summary of the research on how phytohormone signaling affects root system architecture (RSA) in response to nitrogen availability. Overall, this review contributes to identifying recent developments in the interaction between phytohormones and N, as well as serving as a foundation for further study.

Clubroot, a devastating soil borne disease affecting 30%∼50% of Brassicaceae crops worldwide, lacks effective control measures. In the present study, we explored the potential of melatonin (MT) and copper oxide nanoparticle (CuO-NPs) in mitigating clubroot severity in the Brassica rapa ssp. pekinensis. Following 18 h priming with MT, CuO-NPs, or both seeds were grown in controlled environment using synthetic potting mix. Inoculated with Plasmodiophora brassicae spores on 5th day, followed by a soil drench phyto-nano treatment with a week interval. Plants were assessed for various health and growth indices including disease, biometrics, photosynthesis, reactive oxygen species (ROS), antioxidant enzyme activity, hormones and genes expression at onset of secondary clubroot infection using established protocols. Statistical analysis employed ANOVA with Fisher's LSD for significance assessment (P < 0.05). Our results revealed that seed priming with both MT (50 μMol/L) and CuO-NPs (200 mg/L), followed by soil drenching significantly reduced clubroot incidence (38%) and disease index (57%), compared to control treatments. This synergistic effect was associated with enhanced plant growth (shoots: 48% and roots: 59%). Plants treated with both MT and CuO-NPs showed robust antioxidant defenses, significantly increased superoxide dismutase (SOD (25/29%)), catalase (CAT (83/55%)), and ascorbate peroxidase (APX (83/46%)) activity in both shoots/roots, respectively, compared to infected control. Notably, salicylic acid and jasmonic acid levels doubled in treated plants, while stress hormone abscisic acid (ABA) decreased by 80% in roots and 21% in shoots. Gene expression analysis corroborated these findings, showing that the combined treatment activated antioxidant defense genes (SOD, APX and CAT) by 1.9-7.2-fold and upregulated hormone signaling genes JAZ1 (7.8-fold), MYC2 (3.9-fold) and SABP2 (36-fold). Conversely, ABA biosynthesis genes (ABA1 and NCED1) were downregulated up to 7.2-fold, while plant resistance genes NPR1, PRB1 and PDF1.2 were dramatically increased by up to 6.3-fold compared to infected plants. Overall, our combined treatment approach significantly reduces clubroot severity in B. rapa via enhanced antioxidant defenses, improved ROS scavenging, coordinated hormonal regulation and increased pathogen response genes. This study offers promising strategy for developing effective control measures against clubroot in susceptible cruciferous crops.

Introduction: Simple sequence repeats (SSR), also known as microsatellites, are crucial molecular markers in both animals and plants. Despite extensive previous research on SSRs, the development of microsatellite markers in Brassica crops remains limited and inefficient.Methods: Krait software was used to identify microsatellites by genome-wide and marker development based on three recently sequenced basic species of Brassica crops in the triangle of U (Brassica rapa, B. nigra and B. oleracea), as well as three allotetraploids (B. juncea, B. napus and B. carinata) using public databases. Subsequently, the primers and the characteristics of microsatellites for most of them were accordingly designed on each chromosome of each of the six Brassica species, and their physical locations were identified,and the cross-transferability of primers have been carried out. In addition, a B-genome specific SSR marker was screened out.Results: A total of 79341, 92089, 125443, 173964, 173604, and 222160 SSR loci have been identified from the whole genome sequences of Brassica crops within the triangle of U crops, B. rapa (AA), B. nigra (BB), B. oleracea (CC), B. napus (AACC), B. juncea (AABB) and B. carinata (BBCC), respectively. Comparing the number distribution of the three allotetraploid SSR loci in the three subgenomes AA, BB and CC, results indicate that the allotetraploid species have significant reduction in the number of SSR loci in the genome compared with their basic diploid counterparts. Moreover, we compared the basic species with their corresponding varieties, and found that the microsatellite characters between the allotetraploids and their corresponding basic species were very similar or almost identical. Subsequently, each of the 40 SSR primers was employed to investigate the polymorphism potential of B. rapa (85.27%), B. nigra (81.33%) and B. oleracea (73.45%), and B. rapa was found to have a higher cross-transfer rate among the basic species in the triangle of U. Meanwhile, a B-genome specific SSR marker, BniSSR23228 possessing the (AAGGA)₃ sequence characteristics was obtained, and it located in chromosome B3 with a total length of 97 bp.Discussion: In this study, results suggest that the pattern of distribution may be highly conserved during the differentiation of basic Brassica species and their allotetraploid counterparts. Our data indicated that the allotetraploidization process resulted in a significant reduction in SSR loci in the three subgenomes AA, BB and CC. The reasons may be partial gene dominated chromosomal homologous recombination and rearrangement during the evolution of basic diploid species into allotetraploids. This study provides a basis for future genomics and genetic research on the relatedness of Brassica species.

Clubroot, caused by Plasmodiophora brassicae, is a destructive soil-borne disease significantly harming global Brassica crop production. This study employed the Williams and European Clubroot Differential (ECD) and Williams systems to identify the pathotypes of P. brassicae collected from Hangzhou City, Yuhang District and Quzhou City, Kaihua County in Zhejiang Province. Greenhouse and field trials were conducted to evaluate the effects of plastic film covering and four chemical agents on the growth parameters and clubroot severity of the Chinese cabbage cultivar ‘Granaat’. Potential treatment mechanisms on clubroot were explored through a qPCR analysis of the resting spore density and pH measurement of the soil. Furthermore, treatment with 1-napthaleneacetic acid (NAA), a synthetic auxin, was also evaluated for its potential role in suppressing clubroot. The results indicate that the pathotypes of P. brassicae in the two districts were P1, ECD20/31/12, and P3, ECD20/15/4. While an individual application of plastic film covering could not effectively control clubroot, calcium cyanamid, dazomet and ammonium bicarbonate demonstrated significant efficacy in its management. These three agents significantly reduced the resting spore density in the soil, with calcium cyanamid and ammonium bicarbonate also increasing soil alkalinity. Additionally, ammonium bicarbonate promotes lateral root development in ‘Granaat,’ helping infected plants access adequate water and nutrients. However, NAA exhibited no efficacy in clubroot control. Therefore, sustained lateral root development is crucial for effectively resisting P. brassicae invasion. Considering application costs and environmental friendliness, we propose the field application of ammonium bicarbonate as the optimal method for clubroot disease management in Zhejiang Province.

Phytosulfokine (PSK) is a tyrosine-sulfated pentapeptide found throughout the plant kingdom, playing key roles in plant growth, development, and responses to biotic and abiotic stresses. However, there is still a lack of a comprehensive analysis of the BnPSK gene family in Brassica napus. In this study, we conducted a genome-wide identification and characterized 19 BnPSK genes in oil seed plants, which are unevenly distributed across both sub-genomes (A and C). BnPSK proteins ranged from 77 to 99 amino acids (BnPSK3c and BnPSK3d) in length, all belonging to the PSK-α type and containing conserved PSK domains. Synteny analysis revealed that the expansion of the BnPSK gene family is primarily attributed to whole genome duplication, with homology to Arabidopsis thaliana PSK genes. A promoter region analysis identified cis-acting elements related to hormone and stress responses. An expression profile analysis showed that BnPSK genes are highly expressed in roots, leaves, petals, and pollens and are induced by both abiotic stresses and phytohormone application. Furthermore, RT-qPCR assay demonstrated that the expression levels of BnPSK4c, BnPSK5a, and BnPSK5b were significantly enhanced under drought stress (3~5-fold) both in plant roots and leaves following ABA application. Lastly, the application of ABA induced antioxidant activity including SOD, POD, CAT and APX (2~5-fold) and their corresponding genes (3~5-fold), and altered the ROS-signaling in rapeseed plants; also, strong evidence of mitigating drought stress was present. These findings establish a basis for further research into the role of the BnPSK gene family in oilseed plant tolerance against drought stress and underlying molecular mechanisms, offering valuable perspectives for developing novel peptides.