A Flower-Inducing Substance of High Molecular Weight From Cultivated Plants

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Plants initiate flower buds under a variety of conditions, such as specific day-length, age, low temperature and various type of stress. Molecular mechanisms underlying flower-bud formation have not been yet, however, been clarified.We found that the induction or activation of some proteases, probably followed by the degradation of some proteins, is necessary for the induction of flowering in Lemna, suggesting that the products degradated from the proteins by the protease have a promotive effect on flower induction of Lemna. Therefore, we initiated an attempt to isolate and characterize the agent by methods generally used for purification of protein. As a results, we recently discovered a flower-inducing factor of high molecular weight (about 120 kDa). The high-molecular-weight substance could be extracted from soybean, cabbage, rice and pea. The substance was purified to homogeneity. It had characteristic of a polypeptide (a molecular weight of 22 kDa), with an amino-terminal sequence of Leu-Val-Gly-Asn-Thr, and induced formation of flower-buds of Lemna paucicostata 151 at the concentration of 10^<-10> M.At present, we are trying is to determine the order of amino acids in the active substance obtained from soybean, cabbage, rice and pea and investigating how the active substance is produced or activated in plant grown under various flower-bud-inducing conditions, for understanding the mechanism of flower induction at the molecular level. Finally, we investigate whether or not the active substance can control the flowering of cultivated plants.