Nanopore Sequencing Sheds Light on Plant Growth Trigger

Researchers from the Southern University of Science and Technology, under the direction of Prof. Xiaofeng Cao from the Chinese Academy of Sciences’ Institute of Genetics and Developmental Biology, recently reported a new understanding of how light affects plant growth in a study published in the PNAS.

Light is essential to the growth and development of plants because it gives energy and controls many morphological features. The production of polyadenylated full-length transcripts has previously been found to occur through post-transcriptional splicing (PTS).

Because these transcripts’ unspliced introns are kept inside the nucleus, plants may be able to respond swiftly to changes in the environment. The splicing of PTS introns has been found to be dependent on Arabidopsis Protein Arginine Methyltransferase 5 (AtPRMT5), which is involved in the formation of the spliceosome.

However, little is known about the specific mechanisms governing post-transcriptional regulation during the early exposure of immature, etiolated seedlings to light.

The function of post-transcriptional splicing (PTS) in photomorphogenesis - the developmental stage during which seedlings are exposed to light for the first time - was the main focus of this investigation. The scientists discovered that in plant mesophyll cells, light regulates the PTS of genes involved in photosynthesis. Two proteins, Constitutive Photomorphogenic 1 (COP1) and AtPRMT5, co-regulate this process.

Using full-length nascent RNA sequenced by Nanopore, the researchers discovered that 1,411 genes exhibit light-responsive PTS. Six groups were then created from these genes according to the distinct propensities.

The researchers examined seedlings that had been exposed to light for one or six hours as well as those that had been kept in constant darkness using high-throughput single-nucleus RNA sequencing. Ten sub-tissue clusters were successfully classified as a result of this.

Approximately half (3,193 out of 6,224) of the differentially expressed genes (DEGs) analyzed were found to be enriched primarily in mesophyll cells. Interestingly, the researchers found that mesophyll cells significantly expressed genes linked to light-associated PTS.

This study also demonstrated that light-induced PTS in mesophyll cells is regulated by the splicing-related factor AtPRMT5 in concert with the E3 ubiquitin ligase COP1, a major repressor of light signaling pathways. By facilitating photosynthesis, morphogenesis, and chloroplast development, this coordination enables plants to adjust to shifting light conditions.

This work sheds light on how PTS is regulated differently in different cell types, which is crucial for the start of photomorphogenesis. Furthermore, it offers a more profound comprehension of the intricate processes through which plants adjust to their surroundings and interpret signals from various cell types and tissues.