Receptor for Activated C Kinase1B (OsRACK1B) Impairs Fertility in Rice through NADPH-Dependent H2O2 Signaling Pathway

Abstract

The scaffold protein receptor for Activated C Kinase1 (RACK1) regulates multiple aspects of plants, including seed germination, growth, environmental stress responses, and flowering. Recent studies have revealed that RACK1 is associated with NADPH-dependent reactive oxygen species (ROS) signaling in plants. ROS, as a double-edged sword, can modulate several developmental pathways in plants. Thus, the resulting physiological consequences of perturbing the RACK1 expression-induced ROS balance remain to be explored. Herein, we combined molecular, pharmacological, and ultrastructure analysis approaches to investigate the hypothesized connection using T-DNA-mediated activation-tagged RACK1B overexpressed (OX) transgenic rice plants. In this study, we find that OsRACK1B-OX plants display reduced pollen viability, defective anther dehiscence, and abnormal spikelet morphology, leading to partial spikelet sterility. Microscopic observation of the mature pollen grains from the OX plants revealed abnormalities in the exine and intine structures and decreased starch granules in the pollen, resulting in a reduced number of grains per locule from the OX rice plants as compared to that of the wild-type (WT). Histochemical staining revealed a global increase in hydrogen peroxide (H2O2) in the leaves and roots of the transgenic lines overexpressing OsRACK1B compared to that of the WT. However, the elevated H2O2 in tissues from the OX plants can be reversed by pre-treatment with diphenylidonium (DPI), an NADPH oxidase inhibitor, indicating that the source of H2O2 could be, in part, NADPH oxidase. Expression analysis showed a differential expression of the NADPH/respiratory burst oxidase homolog D (RbohD) and antioxidant enzyme-related genes, suggesting a homeostatic mechanism of H2O2 production and antioxidant enzyme activity. BiFC analysis demonstrated that OsRACK1B interacts with the N-terminal region of RbohD in vivo. Taken together, these data indicate that elevated OsRACK1B accumulates a threshold level of ROS, in this case H2O2, which negatively regulates pollen development and fertility. In conclusion, we hypothesized that an optimal expression of RACK1 is critical for fertility in rice plants.

Receptor for Activated C Kinase1B (RACK1B) Delays Salinity-induced Senescence of Rice Leaves through Negative Regulation of Chlorophyll Degradation

“…In a recent study, it was demonstrated that AtRACK1, the Arabidopsis homolog of OsRACK1, participates in leaf senescence [16]. Concurrently, our research revealed that the overexpression of OsRACK1B induces ROS burst as a form of H 2 O 2 through direct interaction with the N-terminal region of OsR-bohD and affects the timing of anther dehiscence, pollen viability, and pollen cell wall integrity [11].…”

Increased panicle nitrogen application improves rice yield by alleviating high‐temperature damage during panicle initiation to anther development

“…Alternatively, Zhang et al (2013) found that the content of malondialdehyde and membrane permeability in the heat‐sensitive rice line were greater than those in the heat‐tolerant line, which was associated with a decrease in the anther dehiscence coefficient and rate of pollen germination. Recently, Rahman et al (2022) reported that hydrogen peroxide (H 2 O 2 ) negatively regulates pollen development and fertility in rice. Similarly, our data showed that HT during panicle initiation also increased the contents of reactive oxygen species (ROS), H 2 O 2 , and malondialdehyde in anthers, particularly in the heat‐sensitive rice variety LYPJ with low pollen and spikelet fertility (Hu, 2021).…”

“…Recently, Rahman et al (2022) reported that hydrogen peroxide (H 2 O 2 ) negatively regulates pollen development and fertility in rice.…”

Receptor for Activated C Kinase1B (RACK1B) Delays Salinity-Induced Senescence in Rice Leaves by Regulating Chlorophyll Degradation

“…Despite a fundamental difference in phosphorylation sites, plant RACK1s appear to be functionally similar to mammalian RACK1 [ 7 , 8 ]. In plants, RACK1 has been implicated in seed germination, root development, flowering, pollen development, and fruit ripening [ 9 , 10 , 11 ]. Mutant analysis in Arabidopsis thaliana and Oryza sativa L. plants revealed that RACK1 plays a crucial role in plants’ response to environmental stress conditions such as drought and salinity [ 12 ].…”

“…In a recent study, it was demonstrated that AtRACK1, the Arabidopsis homolog of OsRACK1, participates in leaf senescence [ 16 ]. Concurrently, our research revealed that the overexpression of OsRACK1B induces ROS burst as a form of H 2 O 2 through direct interaction with the N-terminal region of OsRbohD and affects the timing of anther dehiscence, pollen viability, and pollen cell wall integrity [ 11 ].…”