The Small Auxin-Up RNA Is Involved in the Promotion of Seedling Growth in Rice.

Small auxin-up-regulated RNAs (SAURs) are genes rapidly activated in response to auxin hormones, significantly affecting plant growth and development. However, there is limited information available about the specific functions of SAURs in rice due to the presence of extensive redundant genes. In this study, we found that contains a conserved downstream element in its 3' untranslated region that causes its transcripts to be unstable, ultimately leading to the immediate degradation of the mRNA in rice. In our investigation, we discovered that OsSAUR10 is located in the plasma membrane, and its expression is regulated in a tissue-specific, developmental, and hormone-dependent manner. Additionally, we created mutants using the CRISPR/Cas9 method, which resulted in various developmental defects such as dwarfism, narrow internodes, reduced tillers, and lower yield. Moreover, histological observation comparing wild-type and two mutants revealed that was responsible for cell elongation. However, overexpression of resulted in similar phenotypes to the wild-type. Our research also indicated that plays a role in regulating the expression of two groups of genes involved in auxin biosynthesis () and auxin polar transport () in rice. Thus, our findings suggest that acts as a positive plant growth regulator by contributing to auxin biosynthesis and polar transport.