MED25 Regulates the Alternative Splicing of JAZ Genes through Recruitment of Splicing Factors PRP39 and PRP40

As an important plant hormone, jasmonate (JA) controls resource allocation between growth- and defense-related processes, thus plays a critical role in optimizing plant adaptation to their rapidly changing and often hostile environments. Therefore, both the activation and the deactivation/desensitization of JA responses must be under tight control.

 

It is well recognized that JA-induced production of dominant JAZ splice variants provides a general mechanism to desensitize JA responses. However, it is unclear how plants control the generation of dominant JAZ splice variants to proper levels to prevent excessive and/or uncontrolled desensitization of JA signaling. Prominently, the splicing factors involved in Jas intron-dependent alternative splicing (AS) of JAZ genes and how these splicing factors are recruited remain enigmatic.

 

Recently, a team led by Prof. LI Chuanyou at the Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, revealed a mechanistic function of the Mediator subunit MED25 in coupling the AS of JAZ genes with fine tuning of jasmonate signaling.

 

They found that JA-induced production of dominant JAZ splice variants depends on the functions of the transcription factor MYC2 and MED25. Using affinity purification and mass spectrometry, they found that PRE-mRNA-PROCESSING PROTEIN 39a (PRP39a) and PRP40a, two subunits of the evolutionarily conserved spliceosomal U1 small nuclear ribonucleoprotein particle (snRNP) involved in co-transcriptional AS, are components of MED25-MYC2 functional Complex (MMC).

 

They demonstrated that MED25 controls JA-induced recruitment of PRP39a and PRP40a to JAZ loci to facilitate the full splicing of Jas intron. Therefore, the MED25-PRP39a/PRP40a module plays a critical role in preventing JAZ splice variants-mediated excessive desensitization of JA signaling.

 

This study exemplifies how a Mediator subunit integrates the effects of general splicing factors into a specific signaling pathway to accurately control gene expression.

 

This study supports a scenario that the “multitalented” MED25 acts as a central coactivator of MYC2-dependent transcriptional regulation of JA signaling in a highly organized manner.

 

The paper entitled “Mediator Subunit MED25 Couples Alternative Splicing of JAZ Genes with Fine Tuning of Jasmonate Signaling” was published in The Plant Cell on, Deccember19, 2019 (doi:10.1105/tpc.19.00583).

 

This study was supported by grants from the Chinese Academy of Sciences, the National Key R&D Program of China, and the National Natural Science Foundation of China.

 

 

Contact:

QI Lei

Institute of Genetics and Developmental Biology, Chinese Academy of Sciences

Email: lqi@genetics.ac.cn