Expression of ?-amylase and other gibberellin-regulated genes in aleurone tissue of developing wheat grains

Abstract

Aleurone tissue from freshly harvested immature wheat grains (Triticum aestivum L. cv. Sappo) which is normally unresponsive to gibberellic acid can be made responsive by subjecting the tissue to a pre-incubation treatment in a simple buffered medium prior to the addition of the growth substance. The effectiveness of this treatment is dependent on grain age, with grains less than 15-20 days post anthesis failing to become converted to a responsive state whilst tissue from grains older than this become increasingly susceptible. Tissue from grains of a certain age (approx. 25-28 days post anthesis) produce small amounts of α-amylase following this treatment even in the absence of exogenously applied growth substance. Using different (32)-labelled complementary-DNA probes for α-amylase in wheat it was demonstrated that the failure of freshly harvested tissue to produce α-amylase was correlated with the absence of the appropriate mRNA species. Inability to accumulate α-amylase mRNA in response to gibberellic acid was removed by the pre-iccubation treatment and also by enforced drying. The gibberellin-regulated expression of other unidentified genes also responds to pre-incubation or drying. Induction of gibberellin-responsiveness in immature aleurone cells did not extend to the secretion of acid phosphatase, protease and ribonuclease.

Integrated control of seed maturation and germination programs by activator and repressor functions of Viviparous-1 of maize.

“…2). Our results are consistent with findings that a-amylase genes are not expressed in the developing seed (Nicholls 1979;Cornford et al 1986;Garcia-Maya et al 1990;Oishi and Bewley 1990). Hence, cessation of VP1 expression prior to germination may be necessary to allow induction of a-amylase genes in the germinating seed.…”

“…5). This suggests that expression of VP1 in the developing seed may be, at least in part, responsible for the GA insensitivity of cereal and maize a-amylase genes prior to seed maturity (Nicholls 1979;Cornford et al 1986;Garcia-Maya et al 1990;Oishi and Bewley 1990). In our experiments, VP1 displayed full repressing activity in sln mutant barley seeds (Fig.…”

“…In the developing seed, a-amylase activity is absent prior to seed maturity (Wilson et al 1973;Evans et al 1975). Moreover, a-amylase genes are unresponsive to applied GA (Nicholls 1979;Cornford et al 1986;Garcia-Maya et al 1990;Oishi and Bewley 1990). It has been suggested that the presence of ABA in developing seeds is responsible for the inhibition of a-amylase genes at this developmental stage (King 1976).…”

Water Content, Raffinose, and Dehydrins in the Induction of Desiccation Tolerance in Immature Wheat Embryos

“…Several metabolic processes in seeds are known to be affected by dehydration, which in some cases regulates proteins at the level of gene expression (Cornford et al, 1986;Jiang and Kermode, 1994). Stages in raffinose biosynthesis might be similarly affected, although Blackman et al (1992) concluded from their studies in soybean that galactinol synthase and raffinose synthetase are not likely to be points at which regulation occurs.…”

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

“…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.…”