Cell cycle modulation in the response of the primary root of Arabidopsis to salt stress - PubMed (original) (raw)

Cell cycle modulation in the response of the primary root of Arabidopsis to salt stress

Gerrit West et al. Plant Physiol. 2004 Jun.

Abstract

Salt stress inhibits plant growth and development. We investigated the importance of cell cycle regulation in mediating the primary root growth response of Arabidopsis to salt stress. When seedlings were transferred to media with increasing concentrations of NaCl, root growth rate was progressively reduced. At day 3 after transfer of seedlings to growth medium containing 0.5% NaCl the primary roots grew at a constant rate well below that prior to the transfer, whereas those transferred to control medium kept accelerating. Kinematic analysis revealed that the growth reduction of the stressed roots was due to a decrease in cell production and a smaller mature cell length. Surprisingly, average cell cycle duration was not affected. Hence, the reduced cell production was due to a smaller number of dividing cells, i.e. a meristem size reduction. To analyze the mechanism of meristem size adaptation prior to day 3, we investigated the short-term cell cycle events following transfer to saline medium. Directly after transfer cyclin-dependent kinase (CDK) activity and CYCB1;2 promoter activity were transiently reduced. Because protein levels of both CDKA;1 and CDKB1;1 were not affected, the temporary inhibition of mitotic activity that allows adaptation to the stress condition is most likely mediated by posttranslational control of CDK activity. Thus, the adaptation to salt stress involves two phases: first, a rapid transient inhibition of the cell cycle that results in fewer cells remaining in the meristem. When the meristem reaches the appropriate size for the given conditions, cell cycle duration returns to its default.

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Figures

Figure 1.

Elongation response of the primary root of wild-type (Col-0) plants to different NaCl concentrations. Symbols are means ±

of 24 seedlings.

Figure 2.

Kinematic analysis of the primary root growth of wild-type (Col-0) plants grown in the presence of 0.5% NaCl. Symbols are means ±

(n = 5). A, Velocity profile; B, strain rate; C, cell length.

Figure 3.

p10CKSat-bound kinase activity (A), protein levels of CDKA;1 (B), and CDKB1;1 (C) in the primary root tip of Arabidopsis after transfer to media containing 0 or 0.5% NaCl. 0, 0 h; 2

, 2 h on 0.5% NaCl; 2C, 2 h control; 6

, 6 h on 0.5% NaCl; 6C, 6 h control; 12

, 12 h on 0.5% NaCl; 12C, 12 h control; 24

, 24 h on 0.5% NaCl; 24C, 24 h control; 72

, 72 h on 0.5% NaCl; 72C, 72 h control.

Figure 4.

CYCB1;2 promoter activity in the primary root tip of Arabidopsis as determined by histochemical _GUS_-staining at different times after transfer to media containing 0 or 0.5% NaCl. The numbers indicate the average distance (n = 10 ±

) between the QC and the basal region of the meristem measured by image analysis.

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Cell cycle modulation in the response of the primary root of Arabidopsis to salt stress - PubMed (original) (raw)