Genetic study on the developmental interaction between embryo and endosperm in rice seeds.

利用不同的隐性突变体控制胚大小，研究了水稻种子发育过程中胚乳与胚乳的相互作用。与野生型种子相比，巨型胚突变体具有较大的胚和较小的胚乳。相反，退化胚(Re)突变体具有较小的胚胎(相对较大的胚乳)。此外，突变体无胚性(Emll)在胚胎发育的早期阶段败育，或在成熟的种子中含有微小的球形无器官胚。然而，在种子发育过程中，emll突变体很少能产生对低温条件有反应的野生型胚胎，遗传分析表明这些突变体之间存在上位性，即emll&gt；re&gt；ge。从Ge与其他一些胚性突变体杂交的F_2中分离出的双突变体，球状胚(Gle)或棒状胚(Cle)，其胚胎周围同时有一个大的空腔。在双突变体中观察到的这些表型表明，ge不是直接控制胚胎大小，而是通过调节胚乳发育间接控制胚胎大小。对胚胎和胚乳发育过程中突变基因的研究表明，这些突变基因控制的不是细胞分裂，而是胚胎周围胚乳细胞中淀粉粒等储存物质的积累。

The author examined embryo-endosperm interaction in developing rice seeds using the different recessive mutants control the embryo size. The mutants named as giant embryo (ge) had a large-sized embryo and relatively small-sized endosperm compared with wild type seeds. On the contrary, reduced embryo (re) mutants had a small-sized embryo (relatively large-sized endosperm). Furthermore, the mutants, embryolessl (emll) aborted embryo development in early stages or contained a tiny and globular organless embryo in the matured seed. However, emll mutants were available infrequently to produce wild type embryos responded to the low temperature conditions during seed development.Genetic analysis between the mutants showed the epistasis, i.e. emll >re >ge. Double mutants segregated from F_2 of the crosses between ge and some other embryospecific mutants, globular embryo (gle) or club-shaped embryo (cle) had a gle- or cle - type embryo and simultaneously a large cavity around their embryos. Such phenotypes observed in the double mutants demonstrated that ge could be control not directly but indirectly the embryo size through the regulation of endosperm development.Histological observations. of the mutants during embryo and endosperm developments revealed that these mutant genes control not cell divisions but an accumulation of storage substances such as starch grains in the endosperm cells around the embryo.