Protease activities and elongation growth of excised cotton seed axes during the first 24 hours of imbibition

Abstract

AbstractExcised axes from cotton (Gossypium hirsutumL. cv. M-8, a double haploid) were imbibedin vitrofor 3,6,9,12,18 and 24 h. Data for length, fresh and dry weight and percentage water showed that excised axes undergo a triphasic pattern of growth: an initial burst, a short lag phase and then protracted rapid growth. Analysis of protein content with SDS-PAGE, and of activities of amino-, carboxy- and endopeptidases provided data indicating a direct correlation between major axis elongation growth between 12 and 24 h and enzymatic breakdown of storage proteins (especially those of 48 kDa) by carboxy- and endopeptidase. Data for axes imbibed at 30°C and 0–5°C for 12, 18 and 24 h indicated that a reduction in length and percentage moisture in the cold occurred in parallel with reductions in carboxy- and endopeptidase activities but not in ami-nopeptidase activity. The tentative conclusion is that carboxy- and endopeptidase are probably synthesizedde novoin the axis during imbibition and are important in initial breakdown of storage proteins for axial elongation growth.