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Proteomic profiling reveals differentially expressed proteins associated with amylose accumulation during rice grain filling.

ABSTRACT:

Background

Amylose accumulation in rice grains is controlled by genetic and environmental factors. Amylose content is a determinant factor of rice quality in terms of cooking and eating. Great variations in amylose content in indica rice cultivars have been observed. The current study was to identify differentially expressed proteins in starch and sucrose metabolism and glycolysis/gluconeogenesis pathways and their relationships to amylose synthesis using two rice cultivars possess contrasting phenotypes in grain amylose content.

Results

Synthesis and accumulation of amylose in rice grains significantly affected the variations between rice cultivars in amylose contents. The high amylose content cultivar has three down-regulated differentially expressed proteins, i.e., LOC_Os01g62420.1, LOC_Os02g36600.1, and LOC_Os08g37380.2 in the glycolysis/gluconeogenesis pathway, which limit the glycolytic process and decrease the glucose-1-phosphate consumption. In the starch and sucrose metabolic pathway, an up-regulated protein, i.e., LOC_Os06g04200.1 and two down-regulated proteins, i.e., LOC_Os05g32710.1 and LOC_Os04g43360.1 were identified (Figure 4). Glucose-1-phosphate is one of the first substrates in starch synthesis and glycolysis that are catalyzed to form adenosine diphosphate glucose (ADPG), then the ADPG is catalyzed by granule-bound starch synthase I (GBSS I) to elongate amylose.

Conclusions

The results indicate that decreasing the consumption of glucose-1-phosphate in the glycolytic process is essential for the formation of ADPG and UDPG, which are substrates for amylose synthesis. In theory, amylose content in rice can be regulated by controlling the fate of glucose-1-phosphate.

SUBMITTER: Zhang H

PROVIDER: S-EPMC7561244 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Breeding programs for increasing spikelet number in rice have resulted in compactness of the panicle, accompanied by poor grain filling in inferior spikelets. Although the inefficient utilization of assimilate has been indicated as responsible for this poor grain filling, the underlying cause remains elusive. The current study utilized the suppression subtractive hybridization technique to identify 57 and 79 genes that overexpressed in the superior and inferior spikelets (with respect to each other), respectively, of the compact-panicle rice cultivar Mahalaxmi. Functional categorization of these differentially expressed genes revealed a marked metabolic difference between the spikelets according to their spatial location on the panicle. The expression of genes encoding seed storage proteins was dominant in inferior spikelets, whereas genes encoding regulatory proteins, such as serine-threonine kinase, zinc finger protein and E3 ligase, were highly expressed in superior spikelets. The expression patterns of these genes in the inferior and superior spikelets of Mahalaxmi were similar to those observed in another compact-panicle cultivar, OR-1918, but differed from those obtained in two lax-panicle cultivars, Upahar and Lalat. The results first suggest that the regulatory proteins abundantly expressed in the superior spikelets of compact-panicle cultivars and in both the superior and inferior spikelets of lax-panicle cultivars but poorly expressed in the inferior spikelets of compact-panicle cultivars promote grain filling. Second, the high expression of seed-storage proteins observed in the inferior spikelets of compact-panicle cultivars appears to inhibit the grain filling process. Third, the low expression of enzymes of the Krebs cycle in inferior spikelets compared with superior spikelets of compact-panicle cultivars is bound to lead to poor ATP generation in the former and consequently limit starch biosynthesis, an ATP-consuming process, resulting in poor grain filling.