Callose, found in the cell walls of higher plants such as β-1,3-glucan with β-1,6 branches, is pivotal for both plant development and responses to biotic and abiotic stressors. Plasmodesmata (PD), membranous channels linking the cytoplasm, plasma membrane, and endoplasmic reticulum of adjacent cells, facilitate molecular transport, crucial for developmental and physiological processes. The regulation of both the structural and transport functions of PD is intricate. The accumulation of callose in the PD neck is particularly significant for the regulation of PD permeability. This callose deposition, occurring at a specific site of pathogenic incursion, decelerates the invasion and proliferation of pathogens by reducing the PD pore size. Scholarly investigations over the past two decades have illuminated pathogen-induced callose deposition and the ensuing PD regulation. This gradual understanding reveals the complex regulatory interactions governing defense-related callose accumulation and protein-mediated PD regulation, underscoring its role in plant defense. This review systematically outlines callose accumulation mechanisms and enzymatic regulation in plant defense and discusses PD’s varied participation against viral, fungal, and bacterial infestations. It scrutinizes callose-induced structural changes in PD, highlighting their implications for plant immunity. This review emphasizes dynamic callose calibration in PD constrictions and elucidates the implications and potential challenges of this intricate defense mechanism, integral to the plant’s immune system.

In China, rice is one of the most important cereal crops. Rice bacterial brown leaf spot caused by P. s. pv. syringae is among the most damaging rice diseases in the Heilongjiang Province of China and results in substantial yield losses. In this study, a comprehensive analysis of the pathogen, population structure, and genetic diversity within the species was performed. For this purpose, 176 bacterial isolates of P. s. pv. syringae collected from 15 locations were characterized by using biochemical tests such as the LOPAT test, and genetic characterizations such as multilocus sequence analysis (MLSA) and repetitive PCR, using BOX, REP and ERIC primers. Biochemical testing and detection of syrB genes confirm the presence of P. s. pv. syringae, genetic characterization by MLSA and genetic fingerprinting by repetitive PCR confirmed that high genetic heterogeneity exists in the P. s. pv. syringae isolates, and clustering of the tested isolates and reference strains are related with the same genomospecies 1. This work contributes to the physiological classification of the P. s. pv. syringae isolated from Heilongjiang Province, China, and the results present new data concerning the phylogeny and genetic diversity. This type of study about P. s. pv. syringae has been not reported from this region until now.

Rice false smut (RFS) is pervasive and has emerged as the primary disease affecting rice productivity. Due to the lack of effective chemical control, disease-resistant varieties are the primary method of managing the disease. This study aimed to investigate the influence of biological characteristics such as hyphal growth rate, spore production and germination ability on the pathogenicity of Ustilaginoidea virens. The genetic diversity of 86 U. virens isolates was analyzed, and the tolerant varieties were identified using Rep-PCR molecular markers. The results indicated that among the U. virens isolates analyzed, about 31, 27 and 28 strains exhibited fast, medium and slow mycelium growth rates, respectively. Among the U. virens isolates analyzed, about 33, 27 and 26 strains exhibited strong, medium and weak sporulation abilities, respectively. In addition, among the U. virens isolates analyzed, about 29, 30 and 27 strains exhibited strong, medium and weak spore germination, respectively. No significant correlation was noted between mycelium growth rate and pathogenicity, but sporulation ability, spore germination ability and liquid culture were positively correlated (p < 0.05). Moreover, the genetic structure of U. virens was diverse and complex. There was a significant correlation between the genetic differentiation and pathogenicity of U. virens in Heilongjiang Province, China, with a maximum coefficient of 0.1786 and a minimum coefficient of 0.0129 between Harbin and Suihua, but no significant correlation was found with gene groups or geographical regions. The study found that genes and geographical population variation were primarily within the population, with 95.63% and 4.37% variation (p > 0.05), respectively, while pathogenicity population variation was mainly within the population, with 86.08% and 13.92% variation (p > 0.05), respectively. Pathogenicity had a significant effect on the differentiation of U. virens. Most rice varieties were susceptible, with 3 resistant, 8 moderately resistant, 9 moderately susceptible, 8 susceptible and 12 highly susceptible to RFS disease. Collectively, these results indicate that the tolerance of rice against U. virens is poor, which merits further investigation.

Fusarium oxysporum is one of the main pathogens causing rice seedling blight disease. Revealing its pathogenic mechanism is of great significance for formulating prevention and control strategies for rice seedling blight disease. Copper transporting P-type ATPases (Cu-ATPase) is a large class of proteins located on the plasma membrane that utilize the energy provided by ATP hydrolysis phosphorylation to transport substrates across the membrane. It plays a crucial role in signal transduction, the maintenance of cell membrane stability, and material transport. The main function of Cu-ATPase is to maintain the homeostasis of copper in cells, which is essential for the normal growth and development of organisms. This study utilized the ATMT-mediated gene knockout method to obtain the knockout mutant ∆FoCrpA and the complementation strain ∆FoCrpA-C, which are highly homologous to the P-type heavy metal transport ATPase family in F. oxysporum. The results showed that, compared with the wild-type strain, the knockout mutant ∆FoCrpA had a lighter colony color; a reduced tolerance to copper ion, osmotic, and oxidative stress; a weakened ability to penetrate glass paper; and decreased pathogenicity. However, there was no significant difference in pathogenicity and other biological phenotypes between the complementation strain ∆FoCrpA-C and the wild-type strain. In summary, the FoCrpA gene is involved in osmotic and oxidative stress, affecting the invasion and penetration ability and pathogenicity of F. oxysporum, laying a theoretical foundation for understanding the development and pathogenic mechanism of F. oxysporum.