REGULATION OF SEED GERMINATION AND STAND ESTABLISHMENT - IMPORTANCE OF REPRESSION OF DEVELOPMENTAL PROGRAMS
Identification of triggers of seed germination and seedling growth promotive factors is crucial for the development of new technologies for enhanced stand establishment. Equally important is an understanding of the function of "repressors" in these processes. Repression of the germination program is important as it prevents seeds from unnecessary radicle emergence or risky seedling growth under unfavorable conditions. Elucidating mechanisms involved in the repression of developmental programs in seeds and seedlings will provide us with clues to improve seed germination and stand establishment. In this minireview, the importance of the repression of developmental programs is discussed by examining recent findings from seed biology research. Emergence of the embryo from seed is repressed by surrounding tissues such as the endosperm and testa. This provides the precise control of seed germination in Solanaceae and other species. Repression at the molecular level is also important for seed germination and seedling establishment. Post-transcriptional and -translational regulations play important roles in the repression of developmental programs at certain stages. Degradation of repressor proteins by the ubiquitin-26S proteasome pathway is a central mechanism of gibberellic acid signal transduction in seed dormancy and germination. ABA signaling, which is essential for seed development and seedling responses to the environment, is also mediated by protein degradation. microRNAs (miRNAs) are involved in the repression of transcription factors at the mRNA level during seed germination and seedling growth. Detailed molecular mechanisms involved in the repression of developmental programs in seeds and seedlings are discussed.
Nonogaki, H., Liu, P.-P., Hewitt, J.R. and Martin, R.C. (2008). REGULATION OF SEED GERMINATION AND STAND ESTABLISHMENT - IMPORTANCE OF REPRESSION OF DEVELOPMENTAL PROGRAMS. Acta Hortic. 782, 51-58
ABA, embryo, endosperm, GA, gene expression, testa