Abstract
In C4 plants, mesophyll (M) chloroplasts are randomly distributed in the cells, but bundle sheath (BS) chloroplasts are located in a centripetal or centrifugal position. We previously found that the intracellular arrangement of BS chloroplasts is acquired during cell maturation and can be re-established after disturbance by centrifugation. The intracellular positioning is dependent on actomyosin system and cytosolic protein synthesis but not tubulin or light. In this report, we investigated whether the intracellular positions of M and BS chloroplasts are affected by environmental stresses. When mature leaves of finger millet (Eleusine coracana) were exposed to high-intensity light, M chloroplasts showed light-avoidance movement but BS chloroplasts didn't. The orientation movement of M chloroplasts was also observed under the drought-stress condition. We also observed the similar phenomena in maize. These findings suggest that M and BS cells are also differentiated in regulation system of intracellular chloroplast positioning in response to environmental changes.
