Collada C, Gomez L, Casado R, Aragoncillo C
Departamento de Biotecnologia, Escuela Tecnica Superior de Ingenieros de Montes, Ciudad Universitaria, Madrid, Spain.
Plant Physiol. 1997 Sep;115(1):71-7. doi: 10.1104/pp.115.1.71.
A 20-kD protein has been purified from cotyledons of recalcitrant (desiccation-sensitive) chestnut (Castanea sativa) seeds, where it accumulates at levels comparable to those of major seed storage proteins. This protein, termed Cs smHSP 1, forms homododecameric complexes under nondenaturing conditions and appears to be homologous to cytosolic class I small heat-shock proteins (smHSPs) from plant sources. In vitro evidence has been obtained that the isolated protein can function as a molecular chaperone; it increases, at stoichiometric levels, the renaturation yields of chemically denatured citrate synthase and also prevents the irreversible thermal inactivation of this enzyme. Although a role in desiccation tolerance has been hypothesized for seed smHSPs, this does not seem to be the case for Cs smHSP 1. We have investigated the presence of immunologically related proteins in orthodox and recalcitrant seeds of 13 woody species. Our results indicate that the presence of Cs smHSP 1-like proteins, even at high levels, is not enough to confer desiccation tolerance, and that the amount of these proteins does not furnish a reliable criterion to identify desiccation-sensitive seeds. Additional proteins or mechanisms appear necessary to keep the viability of orthodox seeds upon shedding.
一种20-kD的蛋白质已从顽拗型（脱水敏感型）板栗（Castanea sativa）种子的子叶中纯化出来，其积累水平与主要种子贮藏蛋白相当。这种蛋白质被称为Cs smHSP 1，在非变性条件下形成同型十二聚体复合物，似乎与植物来源的胞质I类小热激蛋白（smHSPs）同源。已获得体外证据表明，分离出的这种蛋白质可作为分子伴侣发挥作用；它以化学计量水平提高化学变性柠檬酸合酶的复性产率，还能防止该酶的不可逆热失活。尽管已推测种子smHSPs在脱水耐受性方面发挥作用，但Cs smHSP 1似乎并非如此。我们研究了13种木本植物的正常性种子和顽拗型种子中免疫相关蛋白的存在情况。我们的结果表明，即使高水平存在Cs smHSP 1样蛋白也不足以赋予脱水耐受性，而且这些蛋白的含量并不能提供一个可靠的标准来鉴定脱水敏感型种子。在正统种子脱落时，似乎还需要其他蛋白质或机制来维持其活力。
