The endoplasmic reticulum stress induced by highly expressed OsrAAT reduces seed size via pre-mature programmed cell death

Abstract

The high accumulation of a recombinant protein in rice endosperm causes endoplasmic reticulum (ER) stress and in turn dramatically affects endogenous storage protein expression, protein body morphology and seed phenotype. To elucidate the molecular mechanisms underlying these changes in transgenic rice seeds, we analyzed the expression profiles of endogenous storage proteins, ER stress-related and programmed cell death (PCD)-related genes in transgenic lines with different levels of Oryza sativa recombinant alpha antitrypsin (OsrAAT) expression. The results indicated that OsrAAT expression induced the ER stress and that the strength of the ER stress was dependent on OsrAAT expression levels. It in turn induced upregulation of the expression of the ER stress response genes and downregulation of the expression of the endogenous storage protein genes in rice endosperm. Further experiments showed that the ER stress response upregulated the expression of PCD-related genes to disturb the rice endosperm development and induced pre-mature PCD. As consequence, it resulted in decrease of grain weight and size. The mechanisms for the detriment seed phenotype in transgenic lines with high accumulation of the recombinant protein were elucidated.

An alternatively spliced heat shock transcription factor, OsHSFA2dI, functions in the heat stress‐induced unfolded protein response in rice

“…6B). To further investigate whether the splicing event of OsbZIP50 mRNA occurs under HS, PCR was performed using a specific set of primers (Zhang et al 2013). The results showed that OsbZIP50 splicing was induced after 15 min of 42°C HS but was not affected by LD treatment (Fig.…”

Cytological, transcriptome and miRNome temporal landscapes decode enhancement of rice grain size

“…1 I and Additional file 1 : Figure S1C), induced probably by expression of positive regulators of PCD from S2 stage onwards (Additional file 1 : Figure S8B and C). Precocious cellularization and PCD are known to reduce GS in rice [ 25 , 26 ], thus restricting GS in SN, and in turn supporting the postulated “Domino effect”. Essential events occurring during seed development, namely cell cycle, cell expansion, storage accumulation, and PCD, appear to be modulated by temporal regulation of phytohormones in the two genotypes creating differences in GS (Figs.…”

“…They can also be transcriptional activators [ 11 ], microtubule-associated proteins [ 22 ], chromatin and histone modifiers [ 23 ], or sucrose transporters [ 24 ]. Any disruption in the timeline of seed development, such as duration of cellularization [ 25 ] and programmed cell death [ 26 ], directly affects GS. Spikelet and cell size of husk also regulate GS [ 8 , 15 , 27 ].…”

Transcriptome Analysis of Rice Embryo and Endosperm during Seed Germination

“…UPR has also been shown to play a role in regulating seed development. For instance, in rice, overexpression of OsrAAT (Oryza sativa recombinant alpha antitrypsin) in the rice endosperm activates UPR and causes chalkiness in the rice grain [37]. Knockout of OsbZIP60 or overexpression of OsbZIP50, OsBiP1, OsBiP2, and OsBiP3 causes various degrees of chalkiness [38].…”