Abstract
SummaryPhosphate (Pi) deficiency in soil system is a limiting factor for rice growth and yield. Majority of the soil phosphorus (P) is organic in nature, not readily available for root uptake. Low Pi‐inducible purple acid phosphatases (PAPs) are hypothesized to enhance the availability of Pi in soil and cellular system. However, information on molecular and physiological roles of rice PAPs is very limited. Here, we demonstrate the role of a novel rice PAP, OsPAP21b in improving plant utilization of organic‐P. OsPAP21b was found to be under the transcriptional control of OsPHR2 and strictly regulated by plant Pi status at both transcript and protein levels. Biochemically, OsPAP21b showed hydrolysis of several organophosphates at acidic pH and possessed sufficient thermostability befitting for high‐temperature rice ecosystems with acidic soils. Interestingly, OsPAP21b was revealed to be a secretory PAP and encodes a distinguishable major APase (acid phosphatase) isoform under low Pi in roots. Further, OsPAP21b‐overexpressing transgenics showed increased biomass, APase activity and P content in both hydroponics supplemented with organic‐P sources and soil containing organic manure as sole P source. Additionally, overexpression lines depicted increased root length, biomass and lateral roots under low Pi while RNAi lines showed reduced root length and biomass as compared to WT. In the light of these evidences, present study strongly proposes OsPAP21b as a useful candidate for improving Pi acquisition and utilization in rice.
Highlights
Given its key role in metabolism and signalling, phosphorus (P) is essential for plant growth and development
We found relatively higher up-regulation of OsPAP21b in roots as compared to shoot tissues under Pi deficiency (Figure 1a)
This indicates that OsPAP21b is a root-preferential phosphate starvation response (PSR) gene
Summary
Given its key role in metabolism and signalling, phosphorus (P) is essential for plant growth and development. Plantavailable P (Pi) is often a limiting factor for crop production in many world soils. About 20 mha of upland area under rice cultivation is Pi deficient (Neue et al, 1990). In major riceproducing areas such as India, ~60% soils have low to medium Pi availability (Murumkar et al, 2015). Application of phosphatic fertilizers can ameliorate soil Pi deficiency. The source of Pi fertilizers, rock phosphate is finite, rapidly depleting and concentrated only in few regions worldwide (Cordell et al, 2009). As rice is one of the major consumers of Pi fertilizers, enhancement of P use efficiency is highly desired for sustainable rice production
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