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Gene-expression profile comparisons distinguish seven organs of maize

ABSTRACT: A maize array was fabricated with 5,376 unique expressed sequence tag (EST) clones sequenced from 4-day-old roots, immature ears and adult organ cDNA libraries. To elucidate organ relationships, relative mRNA levels were quantified by hybridization with embryos, three maize vegetative organs (leaf blades, leaf sheaths and roots) from multiple developmental stages, husk leaves and two types of floral organs (immature ears and silks). Clustering analyses of the hybridization data suggest that maize utilizes both the PEPCK and NADP-ME C(4) photosynthetic routes as genes in these pathways are co-regulated. Husk RNA has a gene-expression profile more similar to floral organs than to vegetative leaves. Only 7% of the genes were highly organ specific, showing over a fourfold difference in at least one of 12 comparisons and 37% showed a two- to fourfold difference. The majority of genes were expressed in diverse organs with little difference in transcript levels. Cross-hybridization among closely related genes within multigene families could obscure tissue specificity. As a first step in elucidating individual gene-expression patterns, we show that 45-nucleotide oligo probes produce signal intensities and signal ratios comparable to PCR probes on the same matrix. Gene-expression profile studies with cDNA microarrays provide a new molecular tool for defining plant organs and their relationships and for discovering new biological processes in silico. cDNA microarrays are insufficient for differentiating recently duplicated genes. Gene-specific oligo probes printed along with cDNA probes can query individual gene-expression profiles and gene families simultaneously. Keywords: other

ORGANISM(S): Zea mays

PROVIDER: GSE141 | GEO | 2003/01/08

SECONDARY ACCESSION(S): PRJNA84533

REPOSITORIES: GEO

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Project description:Maize kernel is an important source of food, feed and industrial raw materials. The illustration of the molecular mechanisms of maize kernel development will be helpful for the manipulation of maize improvements. Although a great many researches based on molecular biology and gecetics have greatly increased our understanding on the kernel development, many of the mechanisms controlling this important process remain elusive. In current study, a microarray with approximately 58,000 probes was used to study the dynamic gene expression during kernel development from the fertilization to physiological maturity. Samples from two consecutive time-points were paired and labeled using different fluorescent dyes (Cy3 and Cy5) and hybridized in the same array. Hybridization of slides was performed according to the manufacturer’s instructions (http://www.maizearray.org/). The hybridized slides were scanned by a Genepix 4000B (Axon, USA). A loop design was applied for running the microarray. Two replicates of each pair of samples were carried out to test both the reproducibility and quality of the chip hybridizations. By comparing six consecutive time-points, namely 1, 5, 10, 15, 25 and 35 days after pollination (DAP), 3,445 differentially expressed genes were identified. These genes were then grouped into 10 clusters showing specific expression patterns using a K-means clustering algorithm. An investigation of function and expression patterns of genes expanded our understanding of the regulation mechanism underlying the important developmental processes, cell division and kernel filling. The differential expression of genes involved in plant hormone signaling pathways suggested that phytohormone might play a critical role in the kernel developmental process. Moreover, regulation of some transcription factors and protein kinases might be involved in the whole developmental process. To obtain the global gene expression profile during maize kernel development, a microarray with approximately 58,000 probes was used. The maize inbred line X178 was planted on the field. Each plant was self-pollinated by hand. The ears were harvested from healthy plants at 1, 5, 10, 15, 25 and 35 days after pollination (DAP), respectively. In order to increase the consistency & uniformity of the isolated kernels, the upper half and about one sixth of ears from the bottom were cut and discarded, the kernels were isolated from the rest part of the ears. Samples at each time-point were collected from at least thirty ears and pooled to represent the line characteristics of X178. Two sub-samples for replication in the microarray analysis were randomly drawn. Samples from two consecutive time-points were paired and labeled using different fluorescent dyes (Cy3 and Cy5) and hybridized in the same array. A loop design was applied for running the microarray. Two replicates of each pair of samples were carried out to test both the reproducibility and quality of the chip hybridizations.

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Gene-expression profile comparisons distinguish seven organs of maize

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