Researchers have discovered how plants regulate DELLA proteins.

      Researchers from the Department of Biochemistry at the Indian Institute of Sciences (IISc) have discovered a long-sought mechanism for regulating the growth of primitive land plants such as bryophytes (a group that includes mosses and liverworts) that was retained in later flowering plants.
       The study, published in the journal Nature Chemical Biology, focused on the non-canonical regulation of DELLA proteins, a master growth regulator that suppresses cell division in embryophytes (land plants).
       Interestingly, bryophytes, the first plants to appear on land approximately 500 million years ago, lack the GID1 receptor, despite producing the phytohormone GA. This raises the question of how the growth and development of these early land plants were regulated.
       Using the liverwort Marchantia polymorpha as a model system, the researchers found that these primitive plants employ a specialized enzyme, MpVIH, which produces the cellular messenger inositol pyrophosphate (InsP₈), to break down DELLA without the involvement of gibberellic acid.
       The researchers used the CRISPR-Cas9 system to knock out the gene encoding the VIH enzyme, confirming its role. Plants lacking functional VIH exhibited severe developmental defects and morphological abnormalities, such as compact leaves, impaired radial growth, and lack of calyxes. These defects were eliminated by modifying the plant genome to produce only one end (the N-terminus) of the VIH enzyme. Using advanced chromatography techniques, the team discovered that the N-terminus contains a kinase domain that catalyzes the production of InsP₈.
       The researchers discovered that DELLA is one of the cellular targets of VIH kinase. Furthermore, they observed that the phenotypes of MpVIH-deficient plants were similar to those of M. polymorpha plants with increased DELLA expression.
       ”At this point, we were excited to understand whether DELLA stability or activity is enhanced in MpVIH-deficient plants,” said Priyanshi Rana, first author and a graduate student in Lahey’s research group. Consistent with their hypothesis, the researchers found that DELLA inhibition can significantly restore the defective growth and development phenotypes of MpVIH mutant plants. These results suggest that VIH kinase negatively regulates DELLA, promoting plant growth and development.
       Research into DELLA proteins dates back to the Green Revolution, when scientists unknowingly exploited their potential to create high-yielding semi-dwarf varieties. Although the details of their work were unclear at the time, modern technology allows scientists to manipulate the functions of these proteins through genetic engineering, effectively increasing crop yields.