Role of desiccation in the termination of expression of genes for storage proteins

Abstract

The final stage of development of orthodox seeds is maturation drying, a process often accompanied by a dramatic decline in storage-protein synthesis When desiccation is imposed prematurely at certain stages prior to the completion of development, a switch in synthetic events is elicited, events unique to development, such as synthesis of storage protein, are terminated, while syntheses associated with germination and growth are initiated We investigated whether desiccation plays a key role in effecting a decline in expression of genes for storage proteins by acting directly upon the regulatory regions of these developmental genes The desiccation responsiveness of the 5' and 3' regulatory regions of the gene for the pea storage protein vicilm was tested in transgemc tobacco seed Chimaeric genes were introduced into tobacco, these genes consisted of the coding region of the reporter gene for [i-glucuronidase (GUS) and 5' and 3' regions from the victim gene, or, as controls, the same regions derived from constitutively expressed genes, presumed to be desiccation-insensitivethose from the cauliflower mosaic virus (35S) and nopalme synthase genes In transgemc seed expressing the gene constructs containing the violin 5' upstream region, GUS activities declined dramatically after imbibition in mature seed and after rehydration of prematurely dried tobacco seed In contrast, GUS activities increased after seed rehydration when the constitutive viral (35S) promoter replaced the vicilin 5' upstream region The 3' downstream region of the gene construct did not "Correspondence significantly affect the patterns of changes in GUS activities after seed rehydration. In studies of transient gene expression in castor bean cotyledons, premature desiccation led to termination of GUS gene expression only when the gene construct contained the vicilin 5' upstream region This region may respond directly to desiccation; alternatively, changes to trans -acting factors important for expression of genes for storage-proteins may occur as a result of drying

Vicilin and Napin Storage-Protein Gene Promoters Are Responsive to Abscisic Acid in Developing Transgenic Tobacco Seed but Lose Sensitivity following Premature Desiccation

“…the sunflower helianthinin storage-protein gene) have been identified (reviewed by Thomas et al,199 1; Thomas, 1993;Nunberg et al, 1994). Our previous studies show that the 5' upstream regions of napin and vicilin storage-protein genes are responsive to desiccation in transgenic tobacco seed (Jiang and Kermode, 1994;Jiang et al, 1995a). For example, GUS gene expression is sensitive to premature desiccation and is down-regulated upon subsequent rehydration in the presence of the 5' regulatory regions of the storage-protein genes but not when under control of the same region from the CaMV 355 gene.…”

“…In many cases, germination and growth of the immature/developing embryo can be elicited precociously by removing the embryo from the surrounding seed tissues, thus bypassing the later stages of development. However, for most seeds, a period of desiccation is the normal terminal event in embryo development and there is now substantial evidence that maturation drying is critica1 to terminating development and overcoming constraints by the maternal environment that maintain seeds in a developmental mode (reviewed by Bewley, 1986a, 1987;Kermode et al, 1986,198913;Kermode, 1990Kermode, , 1995Jiang and Kermode, 1994). This results in a switch in cellular activities from metabolic events associated with seed development (e.g.…”

“…When desiccation is imposed prematurely at certain stages prior to the completion of development, a switch in synthetic events is elicited; events unique to development, such as synthesis of storage protein, are terminated, and syntheses associated with germination and growth are initiated (Evans et al, 1975;Dasgupta and Bewley, 1982;Adams et al, 1983;Kermode and Bewley, 1985a, 1985b, 1986bKermode et al, 1985;Misra and Bewley, 1985;Cornford et al, 1986;Rosenberg and Rinne, 1987;Oishi and Bewley, 1992). In effecting this switch in gene expression, desiccation appears to act primarily at the transcriptional and posttranscriptional levels (Misra and Bewley, 1985;Cornford et al, 1986;Kermode et al, 1989c;Jiang and Kermode, 1994;Jiang et al, 1995aJiang et al, , 1995b. We are interested in examining events at the molecular leve1 caused by drying, which ultimately result in the off-or down-regulation of development-related genes and the onregulation of germinative and postgerminative genes.…”

“…We are interested in examining events at the molecular leve1 caused by drying, which ultimately result in the off-or down-regulation of development-related genes and the onregulation of germinative and postgerminative genes. The 5' upstream regions of napin and vicilin storage-protein genes are responsive to desiccation in transgenic tobacco (Nicotiana tabacum L.) seed (Jiang and Kermode, 1994;Jiang et al, 1995a). For example, GUS gene expression is sensitive to premature desiccation and is down-regulated upon Plant Physiol.…”

The 5[prime] Flanking Regions of Vicilin and Napin Storage Protein Genes Are Down-Regulated by Desiccation in Transgenic Tobacco

“…In many cases, germination and growth of the immature/developing embryo can be elicited precociously by its remova1 from the surrounding seed tissues, thus bypassing the later stages of development. However, for most seeds, a period of desiccation is the normal terminal event in embryo development, and there is now substantial evidence to show that maturation drying is critica1 in terminating development and overcoming constraints by the maternal environment that maintain seeds in a developmental mode (reviewed by Bewley, 1986a, 1987;Kermode et al, 1986, 198913;Kermode, 1990Kermode, , 1995Jiang and Kermode, 1994). This results in a switch in cellular activities from an exclusively developmental program to an exclusively germination/growth-oriented program.…”