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

利用控制胚大小的不同隐性突变体，研究了水稻种子发育过程中胚-胚乳互作。突变体巨胚（ge）与野生型种子相比，胚大，胚乳小。相反，减少胚（再）突变体具有较小的胚（相对较大的胚乳）。此外，无胚突变体（emll）在早期胚胎发育过程中败育，或在成熟种子中含有一个小而球形的无器官胚。但在种子发育过程中，很少有emll突变体能产生对低温敏感的野生型胚，突变体间的遗传分析显示出上位性，即emll >re >ge。在ge与其它一些胚特异突变体杂交的F_2中分离出双突变体，球形胚（gle）或棒形胚（cle）具有gle型或cle型胚，同时胚周围有一个大腔。在双突变体中观察到的这些表型表明，ge不是直接控制胚的大小，而是通过调节胚乳发育间接控制胚的大小。在胚和胚乳发育过程中对突变体的研究表明，这些突变基因不是控制细胞分裂，而是控制胚周围胚乳细胞中淀粉粒等贮藏物质的积累。

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.