Histones and the first cell cycle in maize germination

Abstract

E, 1986, Histones and the first cell cycle in maize germination. -Physiol. Plantarum 68: 259-264.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 putresdne 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 ["Cj-lysine or ["P]-phosphate. The incorporation of either 'C or "P 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. Putresdne stimulated cell division and phosphorylation of the histones. The implications of these findings are discussed.Additional key words -Histone phosphoryiation, histone synthesis, mitotic index, putrescine, Zea mays.

Effect of the auxin, 2‐(2‐methyl‐4‐chloro‐phenoxy)propionic acid, on cell cycle regulation in maize embryonic tissues

“…The mesocotyl was the first and more active tissue showing mitotic figures, followed by seminal and primary root. This result confirms previous findings (Baiza et al 1986).…”

“…The first mitotic figures were observed in mesocotyl meristems, about 18 to 22 h after imbibition, followed by seminal and primary roots. These data confirm previous findings (Baiza et al 1986), and validate the use of the in vitro system as a model for further studies. In both systems, cell division is observed as waves of cells entering the process at the periods stated.…”

“…From the fixed axes, mesocotyl, and primary and seminal root meristems were dissected. Squash preparations were made following Baiza et al (1986), and stained with acetic-orcein (Sharma and Sharma 1980).…”

“…It is not well documented at what phase(s) of the cell cycle embryonic cells of maize seeds are arrested during maturation, nor is there information about the role of auxins in the re-initiation of their first cell cycle. Since it is known that the meristematic cells do not re-enter the cell cycle at once (Baiza et al 1986), it can be suggested that; 1) The cells are arrested at different stages of the cell cycle or 2) that the meristematic cells from specific tissues respond to specific signals for reinitiation of cell division, or 3) that both mechanisms are involved.…”

Biochemical investigations of the nuclear proteins during the transition of root meristems from quiescent to proliferating state in Pisum sativum

“…Early protein synthesis has been shown to occur prior to, or simultaneously with the initiation of cell division due to stored RNA and transcription (BRAY and SMITH, 1985;DELSENG et al, 1981). In maize germination, histone synthesis is initiated far in advance of the actual onset of cell division (BAIZE et al, 1986). In pea embryos it has been shown that, at the time of DNA synthesis, there is an accumulation of non-histone chromosomal proteins, decrease of H, histone concentration whereas the other 4 histones increase in equimolecular amount with the DNA (GRELLET et al, 1977).…”