Knockdown of OsSAE1a affects the growth and development and phosphate homeostasis in rice

SUMOylation is a post-translational modification process that comprises a tandem enzymatic cascade, i.e., maturation, activation, conjugation, and ligation of a small ubiquitin-like modifier, which triggers the modulated activities and transport of the cellular proteins to other areas of the cell. In Oryza sativa (rice), OsSIZ1/2 encoding E3 SUMO ligase exerts regulatory influences on Pi homeostasis and developmental responses. However, the role of OsSAE1a, SUMO E1 activating enzyme, in regulating phosphate (Pi) utilization and/or growth and development is not known in rice and was thus investigated in this study. The qRT-PCR assay revealed a constitutive and variable spatiotemporal expression pattern of OsSAE1a in the vegetative and reproductive tissues and was comparable in the root and shoot grown under different Pi regimes. RNAi-mediated suppression of OsSAE1a exerted variable effects on the concentrations of Pi and total P in different tissues, uptake and distribution of ³²Pi, and relative expression levels of several genes that play pivotal roles in the maintenance of Pi homeostasis. The effects of the mutation in OsSAE1a were also evident in the vegetative and reproductive traits of rice during growth in a hydroponic system and pot soil, respectively. Overall, these results suggest a broad-spectrum role of OsSAE1a in the maintenance of Pi homeostasis and regulating growth and development.