In Vivo Synthesis and Turnover of α-Amylase in Attached and Detached Cotyledons of Vigna mungo Seeds

Abstract

a-Amylase activity increased in attached cotyledons of germinated Vigna muago seeds until the 5th day after imbibition and decreased thereafter, whereas in detached and incubated cotyledons the activity continuously increased and, at the 6th day, reached the value more than three times that of the maximum activity of attached cotyledons. Zymograms of the activities and Ouchterlony double inmunodiffusion test on the activities of attached and detached cotyledons showed that the increase of activity in detached cotyledons was due to the identical enzyme as in attached tissues. a-Amylase contents, determined by single radial immunodiffusion method, changed in paraflel with enzyme activity in both attached and detached cotyledons, which also suggested the de novo synthesis of a-amylase in V. mugo cotyledons.The rate of incorporation of the label from I3Hjleucine into a-amylase and the ratios of dpm in a-amylase/dpm in trichloroacetic acid-insoluble fraction did not show significant difference between attached and detached cotyledons. The results indicated that in attached cotyledons fluctuation of a-amylase activity was regulated by both synthesis and degradation of the enzyme, whereas in detached cotyledons a-amylase was synthesized and accumulated, because of low degrading activity during incubation.In cereal seeds, such as barley, it is well known that gibberellin (GA3) produced in the embryos moves to the aleurone layers and promotes the de novo synthesis and secretion of a-amylase into endosperm. Recent reports suggested that this enzyme induction depends on increase of translatable mRNA for a-amylase (7,15,16), and that this increase is due to a direct enhancement of transcription of a-amylase gene by GA3 (1).In contrast, the mechanism of a-amylase formation in cotyledons of germinating leguminous seeds is not known. Many studies on effects of axis removal or plant hormones have been done, but there are some discrepancies. For example, Yomo and collaborators (24,26) reported that a-amylase activity increases in the cotyledons during seedling growth and during incubation of axisfree cotyledons of pea and bean. This was inconsistent with the findings of others that this increase is partially inhibited by axis removal (3,11,23 processes of seed formation between cereal and leguminous seeds (2), we studied the mechanism of a-amylase formation in cotyledons of germinating bean seeds.We previously reported that amylolytic activity increases in Vigna mungo cotyledons during germination and that the increase is not delayed by axis removal (13). Histochemical observation revealed that amylolytic and proteolytic activities appeared to increase in tissue areas farthest from vascular bundles during germination (14). We also obtained pure a-amylase preparation from cotyledons of V. mungo seedlings using affinity chromatography (8). In the present study, using antibody toward the aamylase obtained by immunization of a rabbit with purified enzyme, we investigated whether the increase of a-amylase is due to de novo s...

Alpha-amylase and protease activities and water relations in germinating sorghum (Sorghum bicolormoench) seeds as affected by animal-waste composts

“…It has been documented that amylase production depends on the accumulation of a specific translatable mRNA (Higgins et al 1982;Koshiba and Minamikawa 1983), and that gibberellic acid (GA) induces the synthesis of new a-amylase mRNA (Muthukrishnan et al 1983). In barley and other cereals GA promotes the formation of protease and other hydrolases in addition to amylase (Yomo and Varner 1973).…”

Biosynthesis of α-Amylase in Vigna mungo Cotyledon

“…We used only detached cotyledons because of their high ability of a-amylase synthesis as described previously (7). Vigna mungo dry cotyledons detached from their embryonic axis were immersed in water for 6 h and then surface sterilized in 1% NaOCI solution for 5 min, rinsed with sterile water, and incubated under aseptic conditions for 4 or 5 d as described previously (7). The (14), and Jackson and Larkins (5).…”

The effect of germination and metallic salts on the stability of enzymes of three high yielding varieties of maize (Zea mays L.) in respect of Bangladesh

“…Germinating seeds generally exhibit high amylase and protease activities. These enzymes were studied in some cereals, legume seeds (Koshiba and Minamikawa, 1983;Morohasi, 1986;Rahman et al, 2006). It was observed that protease activities present in dry seeds were enhanced during germination (Harvey and Oaks, 1974).…”