Abstract
BackgroundPhosphorus (Pi) deficiency induces root morphological remodeling in plants. The primary root length of rice increased under Pi deficiency stress; however, the underlying mechanism is not well understood. In this study, transcriptome analysis (RNA-seq) and Real-time quantitative PCR (qRT-PCR) techniques were combined with the determination of physiological and biochemical indexes to research the regulation mechanisms of iron (Fe) accumulation and callose deposition in rice roots, to illuminate the relationship between Fe accumulation and primary root growth under Pi deficient conditions.ResultsInduced expression of LPR1 genes was observed under low Pi, which also caused Fe accumulation, resulting in iron plaque formation on the root surface in rice; however, in contrast to Arabidopsis, low Pi promoted primary root lengthening in rice. This might be due to Fe accumulation and callose deposition being still appropriately regulated under low Pi. The down-regulated expression of Fe-uptake-related key genes (including IRT, NAS, NAAT, YSLs, OsNRAMP1, ZIPs, ARF, and Rabs) inhibited iron uptake pathways I, II, and III in rice roots under low Pi conditions. In contrast, due to the up-regulated expression of the VITs gene, Fe was increasingly stored in both root vacuoles and cell walls. Furthermore, due to induced expression and increased activity of β-1-3 glucanase, callose deposition was more controlled in low Pi treated rice roots. In addition, low Pi and low Fe treatment still caused primary root lengthening.ConclusionsThe obtained results indicate that Low phosphorus induces iron and callose homeostatic regulation in rice roots. Because of the Fe homeostatic regulation, Fe plays a small role in rice root morphological remodeling under low Pi.
Highlights
IntroductionThe primary root length of rice increased under Pi deficiency stress; the underlying mechanism is not well understood
Phosphorus (Pi) deficiency induces root morphological remodeling in plants
A reddish-brown iron plaque on the rice root surface began to form after treatment by low Pi for 1d (Fig. 1a), and the thickness of iron plaque continuously increased with the prolonging of low Pi treatment time (Fig. 1b and c)
Summary
The primary root length of rice increased under Pi deficiency stress; the underlying mechanism is not well understood. The remodeling mechanism has been reported for Arabidopsis on root morphology in low Pi. Multicopper. The genes involved in Pi transport, phosphatases, and genes pertaining to both primary and secondary metabolism were affected differently by Pi deficiency in rice roots [10]. Overexpression of OsPHR2 in rice mimicked the Pi starvation signal It induces Pi Starvation Induced (PSI), OsIPS1/2 (the gene encoding the signal molecules), miRNAs, SPX domain-containing protein (SPXs), phosphate transporter (PTs), and purple acid phosphatases (PAPs) gene expression, and results in enhanced Pi acquisition [12,13,14,15,16,17]
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