RNA Interference-Mediated Simultaneous Suppression of Seed Storage Proteins in Rice Grains

Abstract

Seed storage proteins (SSPs) such as glutelin, prolamin, and globulin are abundant components in some of the most widely consumed food cereals in the world. Synthesized in the rough endoplasmic reticulum (ER), SSPs are translocated to the protein bodies. Prolamins are located at the spherical protein body I derived from the ER, whereas, glutelins and globulin are accumulated in the irregularly shaped protein bodies derived from vacuoles. Our previous studies have shown that the individual suppression of glutelins, 13-kDa prolamins and globulin caused the compensative accumulation of other SSPs. Herein, to investigate the phenotypic and molecular features of SSP deficiency transgenic rice plants suppressing all glutelins, prolamins, and globulin were generated using RNA interference (RNAi). The results revealed that glutelin A, cysteine-rich 13-kDa prolamin and globulin proteins were less accumulated but that glutelin B and ER chaperones, such as binding protein 1 (BiP1) and protein disulfide isomerase-like 1-1 (PDIL1-1), were highly accumulated at the transcript and protein levels in seeds of the transformants compared to those in the wild-type seeds. Further, the transcription of starch synthesis-related genes was reduced in immature seeds at 2 weeks after flowering, and the starch granules were loosely packaged with various sphere sizes in seed endosperms of the transformants, resulting in a floury phenotype. Interestingly, the rates of sprouting and reducing sugar accumulation during germination were found to be delayed in the transformants compared to the wild-type. In all, our results provide new insight into the role of SSPs in the formation of intracellular organelles and in germination.

iTRAQ-Based Analysis of Proteins Co-Regulated by Brassinosteroids and Gibberellins in Rice Embryos during Seed Germination

“…For instance, expression of both glutelin B2 and prolamin, two storage proteins in rice seeds, declined significantly when endogenous BR or GA biosynthesis was attenuated, suggesting the decreased accumulation of storage proteins in embryos might contribute partly to the defect in seed germination. This is consistent with previous reports that suppression of seed storage proteins by RNAi, including both glutelins and prolamins, delayed rice seed germination [ 42 ]. A recent proteomic study also indicated that the abundance of several glutelin storage proteins was down-regulated during rice seed germination under salt stress [ 43 ].…”

Unique Glutelin Expression Patterns and Seed Endosperm Structure Facilitate Glutelin Accumulation in Polyploid Rice Seed

“…Starch granules in rice seeds with superior quality are smaller, with a distinct polyhedral crystal shape, clear and visible edges and corners, neat and compact arrangement, and a small seed gap (Ji et al 1998 ; Cho et al 2016 ). Conversely, the starch granules of poor quality seeds and in chalky parts of the rice seed are not uniform in size; the polyhedral structure is not well-defined; and the granules are loose (Cho et al 2016 ). The favorable traits in the production of tetraploid rice are high protein and amino acid contents, and low amylose content (Cai et al 2007 ).…”

Seed Metabolome Analysis of a Transgenic Rice Line Expressing Cholera Toxin B-subunit

“…Cho et al . 38 reported that RNAi-mediated suppression of seed storage proteins in rice grains resulted in accumulation of endoplasmic reticulum (ER) chaperones, such as BiP1 and protein disulfide isomerase-like 1–1 (PDIL1-1) 38 . Proteomic analysis of ER-stressed rice seeds revealed changes in the expression of carbohydrate metabolism–related proteins 39 .…”