Kwon S T, Kikuchi S, Oono K
National Institute of Agrobiological Resources Tsukuba, Ibaraki, Japan.
Jpn J Genet. 1992 Aug;67(4):335-48. doi: 10.1266/jjg.67.335.
Rice (Oryza sativa L. var. Nipponbare) suspension callus was exposed to gravity stress at 450,000 g for 2 hours, after which poly(A)+RNA was isolated and a cDNA library was constructed. Three different gravity specific cDNAs, namely, GSC 128, GSC 233 and GSC 381 of 0.67, 0.60 and 0.68 kilobase pairs and transcripts of 1.9, 1.6 and 2.0 kb, respectively, were isolated by differential screening and Northern hybridization. The maximum level of transcript was achieved after 4 hours of exposure to gravity at 450,000 g for GSC 128, 2 hours for GSC 233 and 8 hours for GSC 381 followed by a gradual decrease to undetectable levels with the extension of gravitation time. Callus (GSC 128), shoot and callus (GSC 381) and root and callus (GSC 233) specific expression of transcripts was identified. Although the protection of callus by treatment with ABA, kinetin and sucrose extended the period of expression of mRNA in suspension callus after gravity exposure, the expression of gravity-inducible mRNA was exclusively regulated by the degree of callus viability or survival after the stress. In addition, we demonstrated that the level of GSC 381 transcript was markedly increased by exposing the cell to periodical gravity stress, suggesting that this mRNA is expressed and translated into special proteins which are closely related to the survival of the cell against gravity stress. The sequence of GSC 233 and GSC 381, consisting of 417 and 531 base pairs of the longest open reading frames, encode polypeptides with calculated molecular weights of 15.29 and 19.47 kDa, respectively. A sequence homology search against a data bank revealed that GSC 233 and GSC 381 differed from other stress inducible genes in terms of the coding sequence and expression characteristics.
将水稻（日本晴品种）悬浮愈伤组织在450,000 g的重力胁迫下处理2小时，之后分离出poly(A)+RNA并构建了一个cDNA文库。通过差异筛选和Northern杂交，分离出了三种不同的重力特异性cDNA，即GSC 128、GSC 233和GSC 381，它们的长度分别为0.67、0.60和0.68千碱基对，转录本分别为1.9、1.6和2.0 kb。对于GSC 128，在450,000 g的重力作用下处理4小时后转录本水平达到最高；对于GSC 233，处理2小时后达到最高；对于GSC 381，处理8小时后达到最高，随后随着重力作用时间的延长逐渐降至无法检测的水平。鉴定出了愈伤组织（GSC 128）、芽和愈伤组织（GSC 381）以及根和愈伤组织（GSC 233）中转录本的特异性表达。尽管用脱落酸、激动素和蔗糖处理对愈伤组织的保护延长了重力处理后悬浮愈伤组织中mRNA的表达时间，但重力诱导mRNA的表达完全由胁迫后愈伤组织的活力或存活程度所调控。此外，我们证明，通过使细胞暴露于周期性重力胁迫，GSC 381转录本的水平显著增加，这表明该mRNA被表达并翻译成与细胞抵抗重力胁迫存活密切相关的特殊蛋白质。GSC 233和GSC 381的序列，其最长开放阅读框分别由417和531个碱基对组成，分别编码计算分子量为15.29和19.47 kDa的多肽。对数据库进行的序列同源性搜索显示，GSC 233和GSC 381在编码序列和表达特征方面与其他胁迫诱导基因不同。
