Abstract
Phosphorus (P) deficiency is a major limitation for legume crop production. Although overall adaptations of plant roots to P deficiency have been extensively studied, only fragmentary information is available in regard to root nodule responses to P deficiency. In this study, genome wide transcriptome analysis was conducted using RNA-seq analysis in soybean nodules grown under P-sufficient (500 μM KH2PO4) and P-deficient (25 μM KH2PO4) conditions to investigate molecular mechanisms underlying soybean (Glycine max) nodule adaptation to phosphate (Pi) starvation. Phosphorus deficiency significantly decreased soybean nodule growth and nitrogenase activity. Nodule Pi concentrations declined by 49% in response to P deficiency, but this was well below the 87% and 88% decreases observed in shoots and roots, respectively. Nodule transcript profiling revealed that a total of 2055 genes exhibited differential expression patterns between Pi sufficient and deficient conditions. A set of (differentially expressed genes) DEGs appeared to be involved in maintaining Pi homeostasis in soybean nodules, including eight Pi transporters (PTs), eight genes coding proteins containing the SYG1/PHO81/XPR1 domain (SPXs), and 16 purple acid phosphatases (PAPs). The results suggest that a complex transcriptional regulatory network participates in soybean nodule adaption to Pi starvation, most notable a Pi signaling pathway, are involved in maintaining Pi homeostasis in nodules.
Highlights
Phosphorus (P) is an essential plant macronutrient
The results in this study showed that nodule size, fresh weight, and nitrogenase activity in nodules declined in response to Pi starvation by 27%, 36%, and 45%, respectively (Figure 1a,b,d,e)
Soybean nodules exhibited a superior capability of maintaining Pi homeostasis, as reflected by smaller effects of Pi starvation on nodule Pi concentration than in either soybean leaves or roots
Summary
Phosphorus (P) is an essential plant macronutrient. Phosphate (Pi), the major form of phosphorus acquired by plants, is unevenly distributed in soils, but is readily fixed onto soil particles into unavailable forms (e.g., aluminum-P, iron-P, and calcium-P) [3,4,5]. Intelligent use of moderate amounts of P fertilizer can be beneficial if crops are developed for such conditions. To meet these goals of developing smart crop cultivars with high P utilization efficiency requires further understanding of genetic and molecular mechanisms underlying plant adaptions to P deficiency [8,9,10,11,12]
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