Insulin‐stimulated ribosomal protein synthesis in maize embryonic axes during germination

Abstract

Addition of insulin to maize seed ( Zea mays L. cv. Chalqueño) was found to accelerate germination and seedling growth. Insulin‐stimulated maize axes showed enhancement of S‐methionine incorporation into ribosomal proteins (rp) and mobilization of S 6 rp mRNA into polysomes. Increase in S 6 rp phosphorylation of the small ribosomal subunit (40S) was observed in P‐orthophosphate pulse‐labeled experiments when maize axes were stimulated by insulin. Application of either wortmannin or rapamycin, inhibitors of protein kinases of the insulin transduction pathway, abolished the insulin stimulatory effect on S 6 rp phosphorylation and on ribosomal protein synthesis. The above data are interpreted as an indication of the existence of an insulin‐stimulated signal transduction pathway in maize tissues that is involved in the regulation of translation.