Abstract
OsSIZ1, a small ubiquitin-related modifier (SUMO) E3 ligase, exerts regulatory influences on the developmental responses and phosphate (Pi) homeostasis in rice (Oryza sativa). Whether paralogs OsSIZ1 and OsSIZ2 are functionally redundant or the latter regulates these traits independent of the former is not known. To determine this, in this study, OsSIZ2 was functionally characterized by employing reverse genetic approaches. Although the relative expression of OsSIZ2 was spatiotemporally regulated, it showed constitutive expression in root and leaf blade irrespective of Pi regime. Analysis of T-DNA insertion knockout (ossiz2) and RNAi-mediated knockdown (Ri1-3) mutants revealed positive influences on growth and developmental responses including yield-related traits. On the contrary, these mutants exhibited negative effects on the concentrations of Pi and total P in different tissues. The relative expression levels of some of the genes that are involved in Pi sensing and signaling cascades were differentially modulated in the mutants. Further, attenuation in the expression levels of OsSIZ2 in the roots of ossiz1 and relatively similar trend of the effects of the mutation in OsSIZ1 and OsSIZ2 on growth and development and total P concentration in different tissues suggested a prevalence of partial functional redundancy between these paralogs.
Highlights
The current world population of 7.3 billion is expected to escalate to 9.7 billion by 2050
Post-translational modifications such as sumoylation and ubiquitylation are critical in determining the activity of proteins, which mediate complex regulatory processes that are important for the functioning of a cell[16]
To determine whether expression of OsSIZ2 is spatiotemporally regulated, qRT-PCR was employed for assaying its relative expression levels in different tissues collected from 6 to 16-week-old wild-type rice grown in a pot soil (Fig. 1a)
Summary
The current world population of 7.3 billion is expected to escalate to 9.7 billion by 2050 (www.un.org/en/development). It is imperative to develop plants with higher Pi use efficiency by biotechnological interventions[6,7] In this context, it would be worthwhile to identify some of the molecular entities that influence the maintenance of Pi homeostasis. The mutation in OsSIZ1 triggered elevated concentration of Pi and altered expression levels of several genes involved in the maintenance of Pi homeostasis in ossiz[122] and adversely affected the developmental responses of several reproductive traits[23,24] This raised a pertinent question whether paralogs OsSIZ1 and OsSIZ2 are functionally redundant or the latter exerts independent regulatory influences on the various developmental responses and/or the homeostasis of Pi
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