The 14‐3‐3 protein GF14f negatively affects grain filling of inferior spikelets of rice (Oryza sativa L.)

Abstract

In rice (Oryza sativa L.), later flowering inferior spikelets (IS), which are located on proximal secondary branches, fill slowly and produce smaller and lighter grains than earlier flowering superior spikelets (SS). Many genes have been reported to be involved in poor grain filling of IS, however the underlying molecular mechanisms remain unclear. The present study determined that GF14f, a member of the 14-3-3 protein family, showed temporal and spatial differences in expression patterns between SS and IS. Using GF14f-RNAi plants, we observed that a reduction in GF14f expression in the endosperm resulted in a significant increase in both grain length and weight, which in turn improved grain yield. Furthermore, pull-down assays indicated that GF14f interacts with enzymes that are involved in sucrose breakdown, starch synthesis, tricarboxylic acid (TCA) cycle and glycolysis. At the same time, an increase in the activity of sucrose synthase (SuSase), adenosine diphosphate-glucose pyrophosphorylase (AGPase), and starch synthase (StSase) was observed in the GF14f-RNAi grains. Comprehensive analysis of the proteome and metabolite profiling revealed that the abundance of proteins related to the TCA cycle, and glycolysis increased in the GF14f-RNAi grains together with several carbohydrate intermediates. These results suggested that GF14f negatively affected grain development and filling, and the observed higher abundance of the GF14f protein in IS compared with SS may be responsible for poor IS grain filling. The study provides insights into the molecular mechanisms underlying poor grain filling of IS and suggests that GF14f could serve as a potential tool for improving rice grain filling.

Expression profile of the carbon reserve remobilization from the source to sink in rice in response to soil drying during grain filling

“…ERS1, ERS2, and ETR3 promote starch accumulation in inferior spikelets enhancing the grain filling (Sekhar et al, 2015;Wuriyanghan et al, 2009). One 14-3-3 protein negatively affects inferior spikelet grain filling in rice (Zhang et al, 2019). These genes are good candidates can be used in the rice breeding to increase grain weight.…”

Genome‐wide analysis and phosphorylation sites identification of the 14‐3‐3 gene family and functional characterization of MeGRF3 in cassava

“…; Tables S6, S7 and S8), we were able to verify that MeGRF3 enhances the salt tolerance of transgenic plants, and that phosphorylation of Ser 65 in MeGRF3 significantly influences the ability of MeGRF3 to mediate salt stress responses. In light of recent research reports, we speculated that MeGRF3 may increase the salt tolerance of Arabidopsis by regulating the activity of key proteins involved in the salt overly sensitive (SOS) pathway (Zhang et al ). In addition, MeGRF3 negatively regulated starch metabolism in transgenic Arabidopsis, whereas the phosphomimetic mutation of Ser 65 had little impact on starch metabolism.…”

“…In transgenic potato plants where 14‐3‐3 protein isoforms were repressed, SPS and SS activity was shown to be markedly enhanced (Zuk et al ). Similarly, in GF14f‐RNAi grains a significant increase in SS, AGPase and sucrose synthase, activity was observed, enhancing rice grain development and filling (Zhang et al ). These 14‐3‐3 proteins are also involved in responses to salt, cold and drought stress (Ren et al , Visconti et al , Yang et al ).…”

The Rice Plastidial Phosphorylase Participates Directly In Both Sink And Source Processes

“…Binding of the 14-3-3 to their target proteins can alter the conformation, activity, stability, or intercellular localization [58,59]. 14-3-3 proteins are known to influence grain filling in rice [60,61] , and several starch biosynthetic enzymes such as starch synthase are known targets of 14-3-3 proteins [62,63]. It has been proposed that the dimeric 14-3-3 can act as scaffolding proteins by binding to multiple phosphorylated starch biosynthetic enzymes and keeping them together in a phosphorylation dependent manner [64].…”