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    Root-expressed rice PAP3b enhances secreted APase activity and helps utilize organic phosphate
    (Oxford University Press, 2023) Bhadouria, Jyoti; Mehra, Poonam; Verma, Lokesh; Pazhamala, Lekha T; Rumi, Rumi; Panchal, Poonam; Sinha, Alok Krishna; Giri, Jitender
    Phosphate (Pi) deficiency leads to the induction of purple acid phosphatases (PAPs) in plants, which dephosphorylates organic phosphorus complexes in the rhizosphere and intracellular compartments to release Pi. In this study, we demonstrate that OsPAP3b belongs to group III low molecular weight PAP, and is low Pi responsive, preferentially in roots. The expression of OsPAP3b is negatively regulated with Pi re-supply. Interestingly, OsPAP3b was found to be dual localized to the nucleus and secretome. Furthermore, OsPAP3b is transcriptionally regulated by OsPHR2 as substantiated by DNA-protein binding assay. Through in-vitro biochemical assays, we further demonstrate that OsPAP3b is a functional acid phosphatase with broad substrate specificity. Overexpression of OsPAP3b in rice led to increased secreted APase activity and improved mineralization of organic P sources, reflected in better growth of transgenics compared to wild type when grown on organic P as exogenous P substrate. Under Pi deprivation, OsPAP3b knockdown and knockout lines showed no significant changes in total P content and dry biomass. However, the expression of other phosphate starvation-induced (PSI) genes and the levels of metabolites were found to be altered in the overexpression and knockdown lines. In addition, in-vitro pull-down assay revealed multiple putative interacting proteins of OsPAP3b. Our data collectively suggest that OsPAP3b can aid in organic P utilization in rice. The APase isoforms behavior and nuclear localization indicate its additional role, possibly in stress signaling. Considering its important roles, OsPAP3b could be a potential target for improving low Pi adaptation in rice.
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    Expression of abiotic stress inducible ETHE1-like protein from rice is higher in roots and is regulated by calcium
    (John Wiley & Sons, 2014) Kaur, Charanpreet; Mustafiz, Ananda; Sarkar, Ananda K.; Ariyadasa, Thilini U.; Singla-Pareek, Sneh L.; Sopory, Sudhir K.
    ETHYLMALONIC ENCEPHALOPATHY PROTEIN 1 (ETHE1) encodes sulfur dioxygenase (SDO) activity regulating sulfide levels in living organisms. It is an essential gene and mutations in ETHE1 leads to ethylmalonic encephalopathy (EE) in humans and embryo lethality in Arabidopsis. At present, very little is known regarding the role of ETHE1 beyond the context of EE and almost nothing is known about factors affecting its regulation in plant systems. In this study, we have identified, cloned and characterized OsETHE1, a gene encoding ETHE1-like protein from Oryza sativa. ETHE1 proteins in general are most similar to glyoxalase II (GLYII) and hence OsETHE1 has been earlier annotated as OsGLYII1, a putative GLYII gene. Here we show that OsETHE1 lacks GLYII activity and is instead an ETHE1 homolog being localized in mitochondria like its human and Arabidopsis counterparts. We have isolated and analyzed 1618 bp OsETHE1 promoter (pOsETHE1) to examine the factors affecting OsETHE1 expression. For this, transcriptional promoter pOsETHE1: 5-bromo-5-chloro-3-indolyl-β-D-glucuronide (GUS) fusion construct was made and stably transformed into rice. GUS expression pattern of transgenic pOsETHE1:GUS plants reveal a high root-specific expression of OsETHE1. The pOsETHE1 activity was stimulated by Ca(II) and required light for induction. Moreover, pOsETHE1 activity was induced under various abiotic stresses such as heat, salinity and oxidative stress, suggesting a potential role of OsETHE1 in stress response.