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Larkin, Patrick David.

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Identification and posttranscriptional regulation of genes controlling grain quality in rice (Oryza sativa L.).

Record Type:	Electronic resources : Monograph/item
Title/Author:	Identification and posttranscriptional regulation of genes controlling grain quality in rice (Oryza sativa L.)./
Author:	Larkin, Patrick David.
Description:	93 p.
Notes:	Source: Dissertation Abstracts International, Volume: 60-08, Section: B, page: 3747.
Contained By:	Dissertation Abstracts International60-08B.
Subject:	Biology, Molecular. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=9943522
ISBN:	0599451904

Identification and posttranscriptional regulation of genes controlling grain quality in rice (Oryza sativa L.).
Larkin, Patrick David.

Identification and posttranscriptional regulation of genes controlling grain quality in rice (Oryza sativa L.). - 93 p.

Source: Dissertation Abstracts International, Volume: 60-08, Section: B, page: 3747.

Thesis (Ph.D.)--Texas A&M University, 1999.

Apparent amylose content is the single most important indicator of rice grain quality (Oryza sativa L.) and is a factor of primary consideration in the development of new varieties. Classical genetic studies have identified the waxy locus, encoding the gene for Granule Bound Starch Synthase (GBSS, EC 2.4.1.21) as the primary factor controlling amylose content. Protein gel and Restriction Fragment Length Polymorphism analysis have distinguished two alleles for this locus that correspond to two widely cultivated subspecies, indica and japonica. We have recently demonstrated that the waxy locus can be further subdivided into at least 8 alleles based on a dinucleotide (CT), simple sequence repeat near the transcriptional start site. This increased resolution has allowed us to explain more than 80% of the variation in apparent amylose content in a series of crosses and historically important US rice varieties. Here it is shown that the locus for GBSS is also significantly correlated with starch pasting characteristics, and that this correlation can be traced to a polymorphism in the amino acid sequence of GBSS. Furthermore, we demonstrate that the expression of GBSS is dependent upon a single G to T substitution at the 5' leader intron splice site that is able to distinguish all varieties containing greater than 18% amylose from those with less than 18%. This mutation reduces the efficiency of removal of the leader intron from low amylose varieties. In addition, this G to T polymorphism is associated with differential sensitivity to temperature during the period of grain development. Cultivars with the sequence AGT&barbelow;TATA show a substantial increase in accumulation of mature GBSS transcripts at 18°, compared to 25° or 32°C. The selection of leader intron 5' splice sites is also affected by temperature. A 5' splice site -93 bp upstream from that used in AGG&barbelow;TATA varieties predominates at 18°C. At higher temperature there is increased utilization of a 5' splice site at -1 and a non-consensus site at +1. Utilization of these alternate and non-consensus splice sites can create transcripts with an upstream open reading frame (uORF), a cis-acting signal implicated in RNA transcript degradation. The regulation of GBSS expression is thus shown to be temperature sensitive, and subject to regulation in a post-transcriptional manner.

ISBN: 0599451904Subjects--Topical Terms:

1017719
Biology, Molecular.

Identification and posttranscriptional regulation of genes controlling grain quality in rice (Oryza sativa L.).
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300 $a 93 p.
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500 $a Chair: William D. Park.
502 $a Thesis (Ph.D.)--Texas A&M University, 1999.
520 $a Apparent amylose content is the single most important indicator of rice grain quality (Oryza sativa L.) and is a factor of primary consideration in the development of new varieties. Classical genetic studies have identified the waxy locus, encoding the gene for Granule Bound Starch Synthase (GBSS, EC 2.4.1.21) as the primary factor controlling amylose content. Protein gel and Restriction Fragment Length Polymorphism analysis have distinguished two alleles for this locus that correspond to two widely cultivated subspecies, indica and japonica. We have recently demonstrated that the waxy locus can be further subdivided into at least 8 alleles based on a dinucleotide (CT), simple sequence repeat near the transcriptional start site. This increased resolution has allowed us to explain more than 80% of the variation in apparent amylose content in a series of crosses and historically important US rice varieties. Here it is shown that the locus for GBSS is also significantly correlated with starch pasting characteristics, and that this correlation can be traced to a polymorphism in the amino acid sequence of GBSS. Furthermore, we demonstrate that the expression of GBSS is dependent upon a single G to T substitution at the 5' leader intron splice site that is able to distinguish all varieties containing greater than 18% amylose from those with less than 18%. This mutation reduces the efficiency of removal of the leader intron from low amylose varieties. In addition, this G to T polymorphism is associated with differential sensitivity to temperature during the period of grain development. Cultivars with the sequence AGT&barbelow;TATA show a substantial increase in accumulation of mature GBSS transcripts at 18°, compared to 25° or 32°C. The selection of leader intron 5' splice sites is also affected by temperature. A 5' splice site -93 bp upstream from that used in AGG&barbelow;TATA varieties predominates at 18°C. At higher temperature there is increased utilization of a 5' splice site at -1 and a non-consensus site at +1. Utilization of these alternate and non-consensus splice sites can create transcripts with an upstream open reading frame (uORF), a cis-acting signal implicated in RNA transcript degradation. The regulation of GBSS expression is thus shown to be temperature sensitive, and subject to regulation in a post-transcriptional manner.
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