New Study Reveals the Mechanism of Lamin-like Proteins in Regulating Plant Immunity

Lamina, which underlies the inner nuclear membrane, consists of lamins and their interacting proteins. Lamins are involved in multiple biological processes in metazoan cells, such as DNA replication, gene transcription, and chromatin organization. Although plant has no lamin homolog, the CROWDED NUCLEI (CRWN) family proteins are considered as the best lamin-like candidates that fulfill the roles of lamins in the model plant Arabidopsis thaliana. However, the functions of these proteins are largely unknown.

Dr. FANG Yuda and his colleagues at CAS Center for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, recently revealed a previously unknown function of CRWN proteins in plant immunity. They found that the Arabidopsis crwn1 crwn2 double mutant shows enhanced resistance against virulent bacterial pathogens. Interestingly, they also discovered that both virulent bacteria and salicylic acid can induce proteasome-mediated degradation of CRWN1 proteins.

Using yeast two-hybrid screening, Dr. FANG and his colleagues obtained a novel CRWN1 interacting protein, NAC WITH TRANSMEMBRANE MOTIF1-LIKE9 (NTL9), a NAC transcription factor involved in plant immunity. The interaction between CRWN1 and NTL9 enhances the binding of NTL9 to the promoter of the PATHOGENESIS-RELATED1 (PR1) gene, and inhibits the PR1 expression. Further study demonstrated that the defense related phenotypes of crwn1 crwn2 double mutant are compromised by npr1 in further genetic experiments. These findings revealed a regulatory network which is composed of lamin-like protein CRWN1, NTL9 and NPR1 to regulate the PR1 expression.

Accordingly, in their proposed model, CRWN1 forms a complex with NTL9 and SNI1 to repress PR1 expression and inhibits NPR1 from promoting PR1 transcription; additionally, infection or SA treatment can cause degradation of CRWN1, releasing PR1 from repression.

The study has been published online in Molecular Plant on September 22, 2017.

The study was financially supported by National Key Research and Development Program of China and Chinese Academy of Sciences.

Author contact:
Dr. FANG Yuda, Principal investigator
National key Laboratory of Plant Molecular Genetic
CAS Center for Excellence in Molecular Plant Sciences
Shanghai Institute of Plant Physiology and Ecology
Chinese Academy of Sciences
300 Fenglin Road, Shanghai 200032
Tel: +86-21-54924296
Fax: +86-21-54924015
Email: yfang@sibs.ac.cn