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 some 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, that produces the cellular messenger inositol pyrophosphate (InsP₈), allowing them to break down DELLA without the need for gibberellic acid.
       The researchers found that DELLA is one of the cellular targets of VIH kinase. Moreover, they observed that plants lacking MpVIH mimic the phenotypes of M. polymorpha plants that overexpress DELLA.
       “At this point, we were excited to understand whether DELLA stability or activity is increased 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 inhibiting DELLA significantly rescued the defective growth and development phenotypes of MpVIH mutant plants. These results suggest that VIH kinase negatively regulates DELLA, thereby promoting plant growth and development.
       Research into DELLA proteins dates back to the Green Revolution, when scientists unknowingly exploited their potential to develop high-yielding semi-dwarf varieties. Although the details of how they worked were unclear at the time, modern technology allows scientists to manipulate the functions of these proteins through genetic engineering, effectively increasing crop yields.
       Studying early land plants also provides insights into their evolution over the past 500 million years. For example, although modern flowering plants destabilize DELLA proteins through a gibberellic acid-dependent mechanism, InsP₈ binding sites are conserved. These findings provide insights into the evolution of cell signaling pathways over time.
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