RNA-seq Provides Insights into Sucrose Signaling Re-sponses in White Lupin Roots
White lupin (Lupinus albus) has become a model plant for understanding plant adapta-tions to phosphorus (P) and iron (Fe) deficiency, two major limiting factors for plant productivity. In response to both nutrient deficiencies, white lupin forms cluster roots, bottle-brush-like root structures that aid in P and Fe acquisition from soil. While cluster root function is well studied, not much is known about the signaling pathways involved in sensing and responding to P and Fe deficiency. Sucrose has been identified as a long-distance signal sent in increased concentrations from shoot to root in response to both P and Fe deficiency. Thus, sucrose plays a dual role both as a signal and as a major source of energy for the root. To unravel the responses to sucrose as a signal, we performed Illumina paired-end cDNA sequencing of white lupin roots treated with sucrose for 20, 40 or 80 minutes, compared to untreated controls. We identified 634 up-regulated and 956 down-regulated genes in response to sucrose. Twenty minutes of sucrose treatment showed the most responses, with the ethylene-activated signaling pathway as the most enriched GO (Gene Ontology) category. The number of up-regulated genes went down at 40 min and 80 minutes, and protein dephosphorylation became the most enriched category. Taken together, our findings indicate active responses to sucrose as a signal at 20 minutes after sucrose addition, but fewer responses and potential re-setting of signal transduction pathways by dephosphorylation of proteins at 40 and 80 minutes. Overall design: To unravel responses to sucrose as a signal, we performed Illumina paired-end cDNA sequencing of white lupin roots treated with sucrose for 20, 40, and 80 minutes, compared to untreated controls.