CHANGES IN ALPHA-AMYLASE ACTIVITY DURING PLANT-REGENERATION FROM RICECALLI

Changes in alpha-amylase activity in rice calli during organogenesis w ere investigated in 5 rice varieties that exhibit different abilities for plant regeneration. During organ differentiation in rice callus ti ssues, samples were taken at 5-day intervals up to 35 days and alpha-a mylase (EC. 3.2.1.1) activities were measured. The activity in regener ative calli began to increase 15 to 20 days after transfer to the rege neration medium and were elevated 7-11 fold during the culture period, while the calli transferred to callus maintenance medium did not incr ease and maintained a stable state. The increase in alpha-amylase acti vity in regenerative calli was more rapid in the calli that showed hig her regenerative abilities (Sasanishiki, Tadukan and Tetep) than in th e calli that showed lower regenerative abilities (Fujisaka 5 and Nippo nbare). Correlation coefficients between frequencies of organ differen tiation and alpha-amylase activity in the calli 35 days after transfer to the regeneration medium was highly significant. Expression of a ri ce alpha-amylase gene (RAmy1A) in callus tissues during organ differen tiation was examined by Northern blot and Western blot analyses. Messe nger RNA from the RAmy1A gene, which is a main transcript in germinati ng rice seeds, was highly expressed in the regenerating calli 15 days after transfer. The translated product from the mRNA of the RAmy1A gen e and alpha-amylase isozyme band I (1A and 1B) were highly expressed 2 0 days after transfer, especially in the regeneration medium.