Abstract
BackgroundGenes associated with arsenite uptake and transport in rice plants (i.e., OsLsi1, OsLsi2, OsLsi3, OsLsi6 and OsABCC1) have been identified to date. However, their expression over time during the whole growth period of rice under arsenite stress conditions is still poorly understood. In this study, the dynamics of gene expression associated with arsenite transport and arsenic concentrations in different organs of rice were investigated to determine the critical period(s) of arsenite uptake and translocation regulated by gene expression during the whole growth period.ResultsThe relative expression of OsLsi2 and OsLsi1 in the roots was upregulated and reached its highest value (2-∆∆Ct = 4.04 and 1.19, respectively) at the jointing stage (9 weeks after transplantation), in which the arsenic concentration in roots also was the highest at 144 mg/kg. A range from 45.1 to 61.2% of total arsenic accumulated in the roots during seedling to heading stages (3–16 weeks), which was mainly associated with the relatively high expression of OsABCC1 (1.50–7.68), resulting in arsenic located in the vacuoles of roots. Subsequently, the As translocation factor from root to shoot increased over time from heading to milky ripe (16–20 weeks), and 74.3% of the arsenic accumulated in shoots at the milk stage. Such an increase in arsenic accumulation in shoots was likely related to the findings that (i) OsABCC1 expression in roots was suppressed to 0.14–0.75 in 18–20 weeks; (ii) OsLsi3 and OsABCC1 expression in nodes I, II, and III was upregulated to 4.01–25.8 and 1.59–2.36, respectively, in 16–20 weeks; and (iii) OsLsi6 and OsABCC1 expression in leaves and husks was significantly upregulated to 2.03–5.26 at 18 weeks.ConclusionsThe jointing stage is the key period for the expression of arsenite-transporting genes in roots, and the heading to milky ripe stages are the key period for the expression of arsenite-transporting genes in shoots, both of which should be considered for regulation during safe rice production in arsenic-contaminated paddy soil.Graphical abstract
Highlights
Genes associated with arsenite uptake and transport in rice plants (i.e., OsLsi1, OsLsi2, OsLsi3, OsLsi6 and OsABCC1) have been identified to date
Genes that have been identified to be associated with As(III) uptake and transport in rice plants are the same as those for silicon (Si) uptake and transport because arsenite is a chemical analogue of silicic acid
Arsenic distribution in rice plants during the whole growth period Generally, the total As concentrations in different organs of rice ranked in the following order: root > stem ≥ leaf > husk > brown rice in the +As treatment (Fig. 1)
Summary
Genes associated with arsenite uptake and transport in rice plants (i.e., OsLsi, OsLsi, OsLsi, OsLsi and OsABCC1) have been identified to date. Their expression over time during the whole growth period of rice under arsenite stress conditions is still poorly understood. Understanding the regulations and key period of As(III) uptake and transport by rice is important to developing control strategies for safe rice production in As-contaminated soils. Genes that have been identified to be associated with As(III) uptake and transport in rice plants are the same as those for silicon (Si) uptake and transport because arsenite is a chemical analogue of silicic acid. OsABCC1 can be expressed in roots, stems, leaves and husks of rice, and sequestering As in vacuoles is important in reducing the allocation of As to rice grains [16]
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