The research team of the molecular plant virology revealed a new principle, which the Candidatus Phytoplasma tritici effector SWP12 can suppress wheat resistance
On November 15, 2022, our academic research team of the molecular plant virology published a research paper online, which was entitled “The ‘Candidatus Phytoplasma tritici’ effector SWP12 degrades the transcription factor TaWRKY74 to suppress wheat resistance”. The paper revealed the function and the mechanism of the Candidatus Phytoplasma tritici effector SWP12. The research stated that the Candidatus Phytoplasma tritici effector SWP12 interacted with wheat transcription factor TaWRKY74. It can mediate the degradation of TaWRKY74 by the way of ubiquitin, release the accumulation of plant ROS and improve the liveness of NDH, weaken wheat defence response so as to promote the effect mechanism of phytoplasma infection. Professor Wu, Yunfeng and Associate Professor Zhao, Lei of our college are co-corresponding authors of this paper. Ph.d student Bai, Bixin is the first author of the paper.
The Candidatus Phytoplasma tritici is a prokaryote of circumscribed parasitism of phloem. The Wheat blue dwarf damages winter wheat of spacious northwestern area in our country and threats the food safety because of it. Persistent specialized transmission of the epidemic by the insect vector Psammotettix alienus in the field. When the plant senses the infection of the phytoplasma, the defense system of oxidation is activated. ROS is an important signal molecule and takes part in defense regulation against plant pathogen infection. NDH is a significant constituent part of plant immune warning. Low level NDH caused by silent assembly factor CRR6 makes plant keep high immunological vigilance and spacious resistance to disease. TaWRKY74 not only stimulates the producing of ROS, but damages plant NDH liveness by acting on the promoter of TaCRR6, which is a positive regulatory factor of wheat disease resistance. The Candidatus Phytoplasma tritici secrets the effector SWP12 towards the host during the process of infection. It can target the degradation of TaWRKY74 so as to weaken plant immune reaction and promote the infection of phytoplasma.
During the interaction between wheat and phytoplasma, ROS is induced to produce highly. Expressing effector SWP12 prevents the accumulation of plant ROS evidently and promotes the stimulation of phytoplasma. By the screening of the yeast two-hybrid library, using the protein interaction technique, identify a wheat transcription factor TaWRKY74 characteristically interacted with SWP12. The accumulation of ROS goes ahead apparently, the levels of TaCRR6 transcription and NDH liveness are decreased apparently, the accumulation of phytoplasma is decreased apparently when transient expression of TaWRKY74 is found in grafts. Further silenced TaWRKY74 is found in grafts. The levels of TaCRR6 transcription are unregulated apparently and the accumulation of phytoplasma increases apparently. These results express that TaWRKY74 is an important and positive regulatory factor of wheat defending the infection of phytoplasma.
SWP12 and TaWRKY74 are expressed together compared with TaWRKY74 alone, phytoplasma can accumulate formally in the co-expression plant, the accumulation of ROS and NDH liveness tend to formal level. By the analysis of experimental importing proteasome inhibitor MG-132 and a negative inhibitory protein of ubiquitin chain formation DesGlyGly-ubiquitin (Ub∆GG), the research reveals that SWP12 can improve ubiquitination modification level of TaWRKY74, lead to the ubiquitin- dependent degradation of TaWRKY74. Meanwhile, the TaWRKY74 of degradation resulting in inhibition of TaCRR6 promoter liveness is released, NDH liveness improves subsequently. Further research is found that the wheat of transient silencing TaCRR6 increases resistance to phytoplasma. So, the research identifies an effector SWP12 of reducing plant immune reaction. During promoting the process of self-infection of the phytoplasma, target degradation of host transcription factor TaWRKY74 and improve indirectly the transcription of TaCRR6 and NDH liveness. The clarification of the principle will provide important value for developing a new defensive strategy of wheat blue dwarf.
edited by Hong Wang
checked by Xiaoping Hu