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Laser microdissection-based tissue specific transcriptome analyses reveals novel regulatory network of genes involved in heat-induced grain chalk in rice endosperm.

ABSTRACT: Heat stress occurrence during endosperm development and seed filling forms chalky portion in the limited zone of starchy endosperm of rice grains. In this study, isolation of aleurone, dorsal, central and lateral tissues of developing endosperm by laser-microdissection (LM) coupled with gene expression analysis of 44K microarray was performed to identify key regulatory genes involved in the formation of milky-white (MW) and white-back (WB) chalky grains during heat stress. Gene regulatory network analysis classified the genes changed under heat stress into five modules. the modules of genes changed in developing starchy endosperm corresponding to MW and WB portion under heat stress suggested different regulatory genes involved in each type of grain chalk. The most distinct expression pattern was observed in a M1 and M2 modules where most of the small heat shock proteins and cellular organisation genes being upregulated under heat stress in dorsal aleurone cells and dorsal starchy endosperm zones The histological observation supported the significant increase in cell number and size of dorsal aleurone cells in WB grains. With regard to the central zone of starchy endosperm, preferential downregulation of high molecular weight heat shock proteins (HMW HSPs) including a prominent member encoding for endoplasmic reticulum (ER) chaperones by heat stress were observed, while expression of starch-biosynthesis genes remained unaffected. Characterization of transgenic plants supressing endosperm lumenal binding protein (BiP1), an ER chaperone preferentially downregulated at MW portion under heat stress, showed an evidence of forming the chalky grains without disturbing the expression of starch-biosynthesis genes. The present LM-based comprehensive expression analyses provides novel inferences that HMW HSPs play important role in controlling the redox, nitrogen and amino aicd metabolism in endosperm leading to the formation of MW and WB chalky grains.Keywords ; developing endosperm, gene expression, grain chalkiness, heat stress, laser-microdissection, Oryza sativa.

ORGANISM(S): Oryza sativa

PROVIDER: GSE122115 | GEO | 2018/12/10

REPOSITORIES: GEO

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Project description:This reports the transcript profiling of the aleurone and starchy endosperm layers of wheat seed over 3 time points critical in the development of the aleurone layer. Wheat is a critical food source globally. The aleurone layer develops from the starchy endosperm and is a concentrated source of vitamins and minerals, essential for the germination of the plant embryo. However the molecular mechanisms behind the development of this layer remain poorly understood. Here we present the first direct systematic comparison of the transcriptomes of the aleurone and starchy endosperm tissues of the wheat seed (Triticum aestivum) at time points critical to the development of the aleurone layer of 6, 9 and 14 days post anthesis. Gene expression patterns reflect the changing role of these tissues in seed development. Illumina sequencing gave 25 to 55 million sequence reads per tissue, of the trimmed reads, 70 – 81% mapped to reference expressed sequence transcripts. To quantify transcript abundance, RNA-Seq normalisation was performed to generate RPKM values, these were used in comparative analyses between the tissues at each time point using Kals Z-test. Sequences with significantly different RPKM values were categorised on the basis of tissue and time point expression and functionally annotated using standardised gene ontology vocabularies, revealing two very distinct tissues. In conclusion we show the relationships between and the fundamental biological reprogramming of the two major biologically and economically significant tissues of the wheat seed over time. Understanding these changes in gene expression profiles is essential to mining the potential these tissues hold for human nutrition and contributing to foundational and systems biology of this important crop. Examines the transcript profile of aleurone and starchy endoperm tissues at 6,9 and 14DPA. A minimum of 5 individual seeds from 3 separate spikes from three individual plants were pooled for each tissue preparation.

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Laser microdissection-based tissue specific transcriptome analyses reveals novel regulatory network of genes involved in heat-induced grain chalk in rice endosperm.

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