TEMPERATURE-SENSITIVE MUTATION, EMBRYOLESS-1, AFFECTS BOTH EMBRYO AND ENDOSPERM DEVELOPMENT IN RICE

How the embryo and endosperm interact during seed development is an important subject for elucidating mechanisms of both embryo genesis and endosperm development. We have identified a single temperature-sensitive mutation, embryoless 1 (eml1), affecting both embryo and endosperm development. At a high temperature, eml1 causes embryoless seeds containing large endosperm. Rarely, small embryos with or without organs are formed. At a low temperature, however, the frequency of embryoless seeds drops and seeds are often detected which contain a large embryo and a defective or no endosperm. Thus, in this mutant, embryo size is negatively correlated with endosperm size. Temperature-shift experiments suggest that this mutant becomes insensitive to the temperature change after 4 days post pollination. Accordingly, the seed phenotype of this mutant would be temperature-dependently determined before 4 days after pollination. The negative correlation in size between embryo and endosperm suggests that they developmentally interact from the early stage of seed formation.