Histones and the first cell cycle in maize germination

Abstract

The timing of the onset of cell division during seed germination in maize and the role of histones for this process have been studied. Embryonic axes of maize seeds (Zea mays L. hybrid H‐30) were incubated in a sterile nutrient medium for different periods of time. For some experiments putrescine was also added. Mesocotyl, root tip and scutellar node were dissected at specific periods after incubation and the mitotic indices were determined in these tissues. Embryonic axes were incubated in the same medium either with [14C]‐lysine or [32P]‐phosphate. The incorporation of either 14C or 32P into histones was followed, both in postribosomal supernatant and in nuclei. It was found that during germination, there is specific timing for meristematic cells entering into cell division. Among the tissues tested, the mesocotyl meristem was the first to initiate this process. De novo synthesis of histones was detected as early as after 6 h of imbibition and the rate increased up to 12 h. Putrescine stimulated cell division and phosphorylation of the histones. The implications of these findings are discussed.