Search Results (3)

Rice blast is one of the main diseases of rice, causing severe economic losses to agricultural production; thus, the search for blast resistance is a top priority for rice breeding. When challenged by the blast causal fungus Magnaporthe oryzae the expression level of OsMAPKKK69 gene in rice cultivar Nipponbar was found to increase significantly. Such an induction was also found in a different genetic material, cultivar Shufanggaonuo, indicating that OsMAPKKK69 plays an important role in blast disease response. However, the function of OsMAPKKK69 remains unclear. In this study, wild type ZH11 was selected as the background material to investigate the expression and functions of OsMAPKKK69 in rice disease resistance by constructing knockout mutants. The results showed that OsMAPKKK69 is mainly expressed in four-week-old shoots and localized in cell membrane, cytoplasm, and nucleus. The two allelic knockout mutants, osmapkkk69-1 and osmapkkk69-2, were more resistant to M. oryzae and bacterial blight Xanthomonas oryzae pv. Oryzae (Xoo). Further agronomic trait analysis revealed that the osmapkkk69-1 and osmapkkk69-2 mutants had reduced plant height, smaller grain size, a significant increase in tillering number, but also a significant increase in yield per plant. Our results show that OsMAPKKK69 is involved in the immune response of rice by negatively regulating the resistance to rice blast and blight diseases, and in regulating important agronomic traits. This study lays a foundation for revealing the molecular mechanism of OsMAPKKK69 in the immune response to rice diseases and provides novel genetic resources for rice breeding. Full article

Bacterial leaf streak (BLS) caused by Xanthomonas oryzae pv. oryzicola (Xoc) is one of the most important quarantine diseases in the world. Breeding disease-resistant varieties can solve the problem of prevention and treatment of BLS from the source. The discovery of the molecular mechanism of resistance is an important driving force for breeding resistant varieties. In this study, a BLS-resistant near isogenic line NIL-bls2 was used as the material. Guangxi Xoc strain gx01 (abbreviated as WT) and its mutant strain (abbreviated as MT) with a knockout type III effectors (T3Es) gene were used to infect rice material NIL-bls2. The molecular interaction mechanism of rice resist near isogenic lines in response to infection by different pathogenic strains was analyzed by transcriptome sequencing. The results showed that there were 415, 134 and 150 differentially expressed genes (DEGs) between the WT group and the MT group at 12, 24 and 48 h of post inoculation (hpi). Through GO and KEGG enrichment analysis, it was found that, compared with non-pathogenic strains, the T3Es secreted by pathogenic strains inhibited the signal transduction pathway mediated by ethylene (ET), jasmonic acid (JA) and salicylic acid (SA), and the MAPKK (MAPK kinase) and MAPKKK (MAPK kinase kinase) in the MAPK (mitogen-activated protein kinase) cascade reaction, which prevented plants from sensing extracellular stimuli in time and starting the intracellular immune defense mechanism; and inhibited the synthesis of lignin and diterpenoid phytochemicals to prevent plants from establishing their own physical barriers to resist the invasion of pathogenic bacteria. The inhibitory effect was the strongest at 12 h, and gradually weakened at 24 h and 48 h. To cope with the invasion of pathogenic bacteria, rice NIL-bls2 material can promote wound healing by promoting the synthesis of traumatic acid at 12 h; at 24 h, hydrogen peroxide was degraded by dioxygenase, which reduced and eliminated the attack of reactive oxygen species on plant membrane lipids; and at 48 h, rice NIL-bls2 material can resist the invasion of pathogenic bacteria by promoting the synthesis of lignin, disease-resistant proteins, monoterpene antibacterial substances, indole alkaloids and other substances. Through transcriptome sequencing analysis, the molecular interaction mechanism of rice resistance near isogenic lines in response to infection by different pathogenic strains was expounded, and 5 genes, Os01g0719300, Os02g0513100, Os03g0122300, Os04g0301500, and Os10g0575100 closely related to BLS, were screened. Our work provides new data resources and a theoretical basis for exploring the infection mechanism of Xoc strain gx01 and the resistance mechanism of resistance gene bls2. Full article

The mitogen-activated protein kinase (MAPK) cascades have been validated playing critical roles in diverse aspects of plant biology, from growth and developmental regulation, biotic and abiotic stress responses, to phytohormone signal transduction or responses. A classical MAPK cascade consists of a MAPK kinase kinase (MAPKKK), a MAPK kinase (MAPKK), and a MAPK. From the 75 MAPKKKs, eight MAPKKs, and 15 MAPKs of rice, a number of them have been functionally deciphered. Here, we update recent advances in knowledge of the roles of rice MAPK cascades, including their components and complicated action modes, their diversified functions controlling rice growth and developmental responses, coordinating resistance to biotic and abiotic stress, and conducting phytohormone signal transduction. Moreover, we summarize several complete MAPK cascades that harbor OsMAPKKK-OsMAPKK-OsMAPK, their interaction with different upstream components and their phosphorylation of diverse downstream substrates to fulfill their multiple roles. Furthermore, we state a comparison of networks of rice MAPK cascades from signal transduction crosstalk to the precise selection of downstream substrates. Additionally, we discuss putative concerns for elucidating the underlying molecular mechanisms and molecular functions of rice MAPK cascades in the future. Full article