Carvalho Raquel F, Szakonyi Dóra, Simpson Craig G, Barbosa Inês C R, Brown John W S, Baena-González Elena, Duque Paula
Instituto Gulbenkian de Ciência, 2780-156 Oeiras, Portugal.
The James Hutton Institute, Invergowrie, Dundee DD2 5DA, Scotland, United Kingdom.
Plant Cell. 2016 Aug;28(8):1910-25. doi: 10.1105/tpc.16.00301. Epub 2016 Jul 19.
The ability to sense and respond to sugar signals allows plants to cope with environmental and metabolic changes by adjusting growth and development accordingly. We previously reported that the SR45 splicing factor negatively regulates glucose signaling during early seedling development in Arabidopsis thaliana Here, we show that under glucose-fed conditions, the Arabidopsis sr45-1 loss-of-function mutant contains higher amounts of the energy-sensing SNF1-Related Protein Kinase 1 (SnRK1) despite unaffected SnRK1 transcript levels. In agreement, marker genes for SnRK1 activity are upregulated in sr45-1 plants, and the glucose hypersensitivity of sr45-1 is attenuated by disruption of the SnRK1 gene. Using a high-resolution RT-PCR panel, we found that the sr45-1 mutation broadly targets alternative splicing in vivo, including that of the SR45 pre-mRNA itself. Importantly, the enhanced SnRK1 levels in sr45-1 are suppressed by a proteasome inhibitor, indicating that SR45 promotes targeting of the SnRK1 protein for proteasomal destruction. Finally, we demonstrate that SR45 regulates alternative splicing of the Arabidopsis 5PTase13 gene, which encodes an inositol polyphosphate 5-phosphatase previously shown to interact with and regulate the stability of SnRK1 in vitro, thus providing a mechanistic link between SR45 function and the modulation of degradation of the SnRK1 energy sensor in response to sugars.
感知并响应糖信号的能力使植物能够通过相应地调整生长和发育来应对环境和代谢变化。我们之前报道过，SR45剪接因子在拟南芥幼苗早期发育过程中对葡萄糖信号传导起负调控作用。在此，我们表明，在葡萄糖喂养条件下，拟南芥sr45 - 1功能缺失突变体中能量感应的SNF1相关蛋白激酶1（SnRK1）含量更高，尽管SnRK1转录水平未受影响。与此一致的是，sr45 - 1植株中SnRK1活性的标记基因上调，并且SnRK1基因的破坏减弱了sr45 - 1对葡萄糖的超敏感性。使用高分辨率RT - PCR分析，我们发现sr45 - 1突变在体内广泛靶向可变剪接，包括SR45前体mRNA本身的可变剪接。重要的是，蛋白酶体抑制剂抑制了sr45 - 1中增强的SnRK1水平，表明SR45促进SnRK1蛋白被蛋白酶体降解。最后，我们证明SR45调节拟南芥5PTase13基因的可变剪接，该基因编码一种肌醇多磷酸5 - 磷酸酶，先前已证明其在体外与SnRK1相互作用并调节其稳定性，从而在SR45功能与响应糖对SnRK1能量传感器降解的调节之间提供了一种机制联系。
