Researchers study role of post-transcriptional splicing in plant response to light

In a study published in Proceedings of the National Academy of Sciences On January 30, a research team reports a new understanding of how light affects plant growth.

Light plays a central role in plant growth and development, providing a source of energy and governing various aspects of plant morphology. Post-transcriptional splicing (PTS) has previously been found to generate full-length polyadenylated transcripts. These transcripts, with their unspliced ​​introns, are retained inside the nucleus, potentially allowing plants to rapidly adapt to environmental changes.

Arabidopsis protein Arginine methyltransferase 5 (AtPRMT5), involved in spliceosome formation, was recently identified as being essential for PTS intron splicing.

However, the precise processes that govern post-transcriptional regulation during initial light exposure of etiolated seedlings remain largely unknown.

Led by Professor Cao Xiaofeng of the Institute of Genetics and Developmental Biology of the Chinese Academy of Sciences, in collaboration with researchers from the Southern University of Science and Technology, the researchers focused on the role of post-transcriptional splicing (PTS) in photomorphogenesis. —the stage of development at which seedlings are first exposed to light.

They discovered that light controls the PTS of genes that regulate photosynthesis in plant mesophyll cells. This process is co-regulated by two proteins: AtPRMT5 and Constitutive Photomorphogenic 1 (COP1).

The researchers used Nanopore sequencing of whole nascent RNA to reveal that 1,411 genes undergo light-sensitive PTS. These genes were then classified into six groups based on different propensities.

Later, using high-throughput mononuclear RNA sequencing, the researchers analyzed seedlings kept in continuous darkness and those exposed to light for one or six hours. This led to the successful classification of 10 subtissue groups.

Analysis of differentially expressed genes (DEGs) revealed that approximately half (3,193 of 6,224) of these DEGs were primarily enriched in mesophyll cells. Intriguingly, the researchers found that genes involved in light-associated PTS showed significant expression in mesophyll cells.

This work further established that the splicing-related factor AtPRMT5 functions in tandem with the E3 ubiquitin ligase COP1 (a primary repressor of light signaling pathways) to coordinate light-induced PTS in mesophyll cells. This coordination facilitates chloroplast development, photosynthesis, and morphogenesis, allowing plants to adapt to changing light conditions.

This study provides important insights into the cell type-specific regulation of PTS, which is essential for the onset of photomorphogenesis. It also provides insight into the complex mechanisms by which plants acclimatize and transduce environmental signals across specific cell types and tissues.