Arabidopsis ribosomal proteins control developmental programs through translational regulation of auxin response factors.

This article provides a nice example of a how an incompletely understood form of gene regulation plays a significant role in several auxin-based plant developmental programs. Many responses to auxin have come to be understood in terms of how it activates a diverse family of auxin response factors (ARFs), which in turn act as transcription factors to determine auxin-dependent patterns of gene expression. Previous studies have shown that ribosomal protein mutants compromise certain auxin-dependent programs, suggesting a role for translational regulation. In the current study, mutants to RPL4A, RPL4D and RPL5A, were shown to decrease the expression of ARF5 and ARF7 proteins. This decrease could be attributed to the presence of upstream open reading frames (uORFs) in ARF5 and ARF7 mRNAs that reduce translation of downstream coding regions. Together, this work indicates that uORFs can act as cis-acting elements to regulate the translation of downstream ORFs that are part of an auxin response pathway. The frequent occurrence of uORFs in mRNAs of many gene families suggests their wider significance as a means to regulate gene expression.