Dulson J, Bewley J D, Johnston R N
Department of Biology, University of Calgary, Calgary, Alberta T2N 1N4, Canada.
Plant Physiol. 1988 Jul;87(3):660-5. doi: 10.1104/pp.87.3.660.
The production of mannanase, a cell-wall-degrading carbohydrase, can be manipulated in isolated lettuce (Lactuca sativa cv Grand Rapids) endosperms by changes in the volume of buffer in which they are incubated. The enzyme is produced when endosperms are incubated in a large volume, but not when incubated in a small volume, which is suggestive that an endogenous, diffusible inhibitor of mannanase production is being lost from the endosperms in a large volume (JD Bewley, P Halmer 1980/1981 Israel J Bot 29: 118-132). We have investigated the possibility that the phytohormone abscisic acid (ABA) is involved in this regulation of mannanase production in isolated lettuce endosperms. We find several correlations between the presence of the endogenous inhibitor and of ABA, i.e. (a) a ;leachate' prepared from isolated lettuce endosperms induces synthesis of ABA-specific proteins in barley aleurone layers, indicating that incubation of endosperms in a large volume results in the diffusion of ABA therefrom into the surrounding medium; (b) fractionation of the components of a leachate by either polyvinylpyrrolidone-chromatography of C(18) reversed-phase high performance liquid chromatography fails to separate the endogenous inhibitor from authentic ABA; and (c) changes in the incubation volume of endosperms result in changes in the amount of extractable ABA in the endosperms, as detected by ELISA. These results are consistent with a role for endogenous ABA in the regulation of mannanase production in isolated lettuce endosperms.
甘露聚糖酶是一种可降解细胞壁的碳水化合物酶，在离体的生菜（Lactuca sativa cv Grand Rapids）胚乳中，通过改变其孵育缓冲液的体积可调控该酶的产生。当胚乳在大量缓冲液中孵育时会产生这种酶，而在少量缓冲液中孵育时则不会，这表明胚乳中一种内源性的、可扩散的甘露聚糖酶产生抑制剂在大量缓冲液中会从胚乳中流失（JD Bewley，P Halmer 1980/1981，Israel J Bot 29：118 - 132）。我们研究了植物激素脱落酸（ABA）参与离体生菜胚乳中甘露聚糖酶产生调控的可能性。我们发现内源性抑制剂与ABA的存在之间存在若干相关性，即：（a）从离体生菜胚乳制备的“渗出液”可诱导大麦糊粉层中ABA特异性蛋白的合成，这表明胚乳在大量缓冲液中孵育会导致ABA从胚乳扩散到周围培养基中；（b）通过聚乙烯吡咯烷酮色谱法或C（18）反相高效液相色谱法对渗出液的成分进行分级分离，均无法将内源性抑制剂与纯ABA分开；（c）胚乳孵育体积的变化会导致胚乳中可提取ABA量的变化，这通过酶联免疫吸附测定法得以检测。这些结果与内源性ABA在离体生菜胚乳中甘露聚糖酶产生调控中的作用一致。
