Abstract
myo-Inositol monophosphatase (IMP) is an essential enzyme in the myo-inositol metabolic pathway where it primarily dephosphorylates myo-inositol 1-phosphate to maintain the cellular inositol pool which is important for many metabolic and signalling pathways in plants. The stress-induced increased accumulation of inositol has been reported in a few plants including chickpea; however, the role and regulation of IMP is not well defined in response to stress. In this work, it has been shown that IMP activity is distributed in all organs in chickpea and was noticeably enhanced during environmental stresses. Subsequently, using degenerate oligonucleotides and RACE strategy, a full-length IMP cDNA (CaIMP) was cloned and sequenced. Biochemical study revealed that CaIMP encodes a lithium-sensitive phosphatase enzyme with broad substrate specificity, although maximum activity was observed with the myo-inositol 1-phosphate and l-galactose 1-phosphate substrates. Transcript analysis revealed that CaIMP is differentially expressed and regulated in different organs, stresses and phytohormones. Complementation analysis in Arabidopsis further confirmed the role of CaIMP in l-galactose 1-phosphate and myo-inositol 1-phosphate hydrolysis and its participation in myo-inositol and ascorbate biosynthesis. Moreover, Arabidopsis transgenic plants over-expressing CaIMP exhibited improved tolerance to stress during seed germination and seedling growth, while the VTC4/IMP loss-of-function mutants exhibited sensitivity to stress. Collectively, CaIMP links various metabolic pathways and plays an important role in improving seed germination and seedling growth, particularly under stressful environments.
Highlights
Introduction myoInositol is a six carbon cyclohexane hexitol and has a diverse role in plant biology
The data revealed that seedlings subjected to abiotic stresses showed higher Inositol monophosphatase (IMP) activity compared with normally grown seedlings (Fig. 1), the stressinduced up-regulation of IMP activity varied with different stresses
Besides an essential role in the myo-inositol metabolic pathway, IMP is reported to participate in various metabolic pathways like galactose metabolism in mammals, gluconeogenesis in methanogens, and ascorbate biosynthesis in Arabidopsis (Parthasarathy et al, 1997; Stec et al, 2000; Torabinejad et al, 2009)
Summary
Introduction myoInositol is a six carbon cyclohexane hexitol and has a diverse role in plant biology. IMP is reported to dephosphorylate other inositol phosphate compounds such as the breakdown products of phosphoinositides (Gillaspy et al, 1995; Quintero et al, 1996; Loewus and Murthy, 2000) This enzyme is essential because IMP is required for both de novo synthesis as well as the recycling of inositol and can be a critical and potential regulatory point for all pathways that use free inositol
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
