Light serves as the fundamental element for the existence of all living organisms. It is not only a vital energy source for plant growth and development but also directly regulates these processes. The regulation of plant growth and development by light is known as photomorphogenesis, which is characterized in Arabidopsis thaliana by the inhibition of hypocotyl elongation, disappearance of apical hook, chloroplast development, and other phenomena. COP1 (CONSTITUTIVE PHOTOMORPHOGENIC 1) is a central negative regulator in plant photomorphogenesis. As an E3 ubiquitin ligase, COP1 inhibits photomorphogenesis by ubiquitinating and degrading a series of substrates. Additionally, COP1 plays a wide-ranging role in regulating processes such as flowering, stomatal development, and circadian rhythms. Therefore, the proper functioning of COP1 is crucial for plant growth and development. To identify additional signaling pathways of COP1, researchers performed EMS mutagenesis on the cop1-6 mutant (a weak allele) and screened for genetic suppressors that could restore cop1-6 phenotypes under dark conditions. Thirteen dominant suppressors of cop1-6 were obtained, and through gene mapping and whole-genome resequencing, six dominant cop1-6 suppressor genes (DCS1-DCS6) were successfully cloned. These findings have recently been published in the prestigious international journal Nature Communications.

 

Intron retention (IR) is the most common alternative splicing event in plants and plays a crucial role in gene expression regulation. It has been discovered that intron-retained transcripts (IRTs) can remain in the nucleus, avoiding translation into new proteins or degradation. Under external stimuli or developmental changes, these IRTs stored in the nucleus can be processed by splicing and transported to the cytoplasm for translation, thereby allowing rapid responses to external signals and coordinating plant growth and development at the transcript level.

 

This study demonstrates the involvement of COP1 in light-mediated mRNA alternative splicing, primarily intron retention (IR), to coordinate photomorphogenesis in Arabidopsis thaliana seedlings. Light regulates the precise control of photomorphogenesis in Arabidopsis seedlings by modulating the IR of genes encoding members of the light signaling pathway, such as PIF4, RVE1, and ABA3. This process depends on COP1 and is regulated by the spliceosome complex. The identified proteins, DCS1-DCS6, are all components of the Arabidopsis spliceosome. COP1 directly interacts with the plant-specific spliceosome component protein DCS1 and promotes its ubiquitination and degradation, thereby regulating the functional state of the spliceosome complex. Thus, this study reveals a novel molecular mechanism of light-COP1-spliceosome module in regulating plant photomorphogenesis.

 

 

Dr. Hua Zhou, a research assistant professor at the Southern University of Science and Technology, is the first author of this paper, and Academician Xing Wang Deng is the corresponding author. The Southern University of Science and Technology is the primary affiliation of the first author, while Peking University Institute of Advanced Agricultural Science (PKU-IAAS) is the second affiliation. Research Professor Guochen Qin, Ph.D. student Haiyue Zeng, as well as research assistant Ying Fu from PKU-IAAS participated in this research work. Collaborative institutions involved in this study include Southwest University, Nanjing Agricultural University, Lanzhou University, Nanjing Normal University, South China Agricultural University, Brookhaven National Laboratory in the United States, and Hainan Academy of Agricultural Sciences. This research received support from the National Natural Science Foundation of China, the Peking University-Tsinghua University Joint Center for Life Sciences, the Southern University of Science and Technology, and the Shenzhen Science and Technology Planning Project.

Paper link: https://www.nature.com/articles/s41467-024-49571-9