Studies have found rice koji disease resistance genes

Before the 80s of the 20th century, rice koji disease occurred sporadically, and usually occurred in rice harvest years, so it was also called "abundant grain disease"
by the folk.
Before the 80s of the 20th century, rice koji disease occurred sporadically, and usually occurred in rice harvest years, so it was also called "abundant grain disease"
by the folk.
In recent years, the occurrence of rice koji disease has been widely distributed in more than 40 rice-growing countries or regions in Asia, America, Africa and Europe, especially in China, with an average annual occurrence area of more than
45 million mu.
Rice koji disease not only affects rice yield and rice quality, but also produces mycotoxin pollution that endangers human and animal health
.
Oryzae specifically infects rice flower organs in the late stage of rice panicle to prevent flowering and fertilization and seed formation
.
Since the pathogenesis of rice koji disease is extremely dependent on environmental conditions, the use of forward genetics to identify rice koji disease resistance genes has been slow, and there is still a lack of resistance gene resources for rice koji disease resistance breeding
。 Professor Wang Wenming's team from the State Key Laboratory of Crop Gene Resources Exploration and Utilization in Southwest China published a paper entitled "Enhanced production of OsRACK1A, an effector-targeted scaffold protein that promotes OsRBOHB-mediated ROS production, confers rice floral resistance to false smut disease without yield penalty"
.
In this paper, a novel pathogenic mechanism mediated by cytoplasmic effectors of Aspergillus oryzae was reported, and a gene
that significantly improved rice koji disease resistance without affecting rice yield was mined using effectors as molecular probes.
The study found that Aspergillus oryzae secretes a cytoplasmic effector UvCBP1 to promote infestation
of rice flower vessels.
Mechanistically, UvCBP1 interacts with the rice scaffold protein OsRACK1A to compete for its interaction with the NAPDH oxidase OsRBOHB, resulting in a decrease in the phosphorylation level of OsRBOHB, thereby reducing the production of reactive oxygen species (ROS) and susceptibility to rice
。 Although natural variation analysis did not find OsRACK1A variants that could evade UvCBP1 targeting, the promoter of OsRACK1A had rich polymorphisms, and association analysis showed that a large fragment insertion of 7873-bp in the promoter of OsRACK1A was significantly negatively correlated
with the transcription level and resistance of OsRACK1A.
Genetic analysis of recombinant inbred populations and single-fragment substitution lines further confirmed this result
.
Importantly, overexpression of OsRACK1A by transgenic means not only improved the resistance of rice to rice koji disease, but also had no significant effect
on the main agronomic traits and yield of rice.
Therefore, this study not only reveals a new pathogenic mechanism of plant flower organ pathogens, but also provides valuable genetic resources
for the cultivation of high-yield rice resistant to koji disease.
Li Guobang, postdoctoral fellows from the State Key Laboratory of Crop Gene Resources Exploration and Utilization in Southwest China, He Jiaxue and Wu Jinlong, master's students, and Dr.
Wang He, a young teacher, are the co-first authors of the paper, and Professor Wang Wenming and Professor Fan Jing are the co-corresponding authors
.
In addition, Professor Chen Xuewei, Professor Li Shigui, Professor Huang Fu, Professor Wu Xianjun, Professor Xu Zhengjun and other teams of Sichuan Agricultural University provided support
for this research.
The research was supported
by the National Natural Science Foundation of China, the Sichuan Youth Science and Technology Innovation Research Team, and the Sichuan Agricultural University Double Support Program.

Pattern of UvCBP1-mediated pathogenesis of Aspergillus oryzae effector and mechanism of resistance to rice koji disease mediated by rice scaffold protein OsRACK1A