Unlocking Barley's Phosphorus Efficiency: The Emerging Role of RNA Processing in Low-Phosphorus Adaptation

Improving phosphorus use efficiency (PUE) in crops is critical for sustainable agriculture. Although the transcriptional regulation of phosphate starvation responses, centered on regulators such as the PHR1 and SPX proteins, is well established, the post-transcriptional mechanisms remain incompletely understood. This gap hinders a comprehensive view of how plants adapt to low-P conditions. This review synthesizes current knowledge on the gene regulatory networks involved in low-P adaptation in barley, with a specific focus on the emerging role of RNA processing. It highlights the limited knowledge of how alternative splicing contributes to this response. AS provides a rapid and energy-efficient means of fine-tuning gene expression, expanding proteome diversity and enabling more sophisticated adaptation mechanisms than the relatively binary "on/off" mode of transcriptional control. Several core regulators of AS, including serine-arginine-rich proteins and hnRNPs, have been identified, with the former discussed in detail and illustrated with key examples. Building on the advanced mechanistic insights into AS gained from model crops such as rice, this review proposes a predictive framework to prioritize research targets and experimental strategies. Such an approach can accelerate the discovery of analogous mechanisms in barley, thereby bridging a critical knowledge gap and advancing strategies to improve PUE in this important cereal crop.