Microgravity modifies the cell cycle in the lentil root meristem

Abstract

In order to investigate the effects of microgravity on the cell cycle, lentil seedlings were grown in space as follows: 1 - in microgravity for 29h (Fμg), 2 - on the 1g centrifuge (F1g), 3 - in microgravity for 25h and then on the 1g centrifuge for 4h (Fμ-1g), 4 - on the 1g centrifuge for 25h and then in microgravity for 4h (F1g+μg). There were no statistical differences in mean root length after 29h in the four samples. The DNA content of nuclei in the root meristem was estimated by image analysis after sectioning and staining by the Feulgen technique. Three different regions, each of 0.2mm length ( a, b, c), were distinguished basal to the root cap junction (RCJ). No difference in the distribution of nuclear DNA contents was found in region c (the furthest from the RCJ) in all four growth conditions. However, the nuclear DNA distributions were different in regions a and b in microgravity and on the 1g centrifuge (there were more cycling cells in 1g than in 1μg). When roots were grown in 1g and transferred to microgravity (F1g+μg), the proportion of cycling cells was increased. In the (Fμg+1g) sample, by contrast, the cell cycle was not modified by the transfer from 1μg to 1g. Microgravity perturbed the cell cycle by lengthening the G1 phase in the lentil root meristem