Abstract：
How microgravity in space influences plant cell growth is an important issue for plant cell biology as well as space biology. We investigated the role of cortical microtubules in the stimulation of elongation growth in Arabidopsis (Arabidopsis thaliana) hypocotyls under microgravity conditions with the Resist Tubule space experiment. The epidermal cells in the lower half of the hypocotyls of wild-type Columbia were longer in microgravity than at on-orbit 1 g, which precipitated an increase in the entire hypocotyl length. In the apical region, cortical microtubules adjacent to the outer tangential wall were predominantly transverse to the long axis of the cell, whereas longitudinal microtubules were predominant in the basal region. In the 9th to 12th epidermal cells (1 to 3 mm) from the tip, where the modification of microtubule orientation from transverse to longitudinal directions (reorientation) occurred, cells with transverse microtubules increased, whereas those with longitudinal microtubules decreased in microgravity, and the average angle with respect to the transverse cell axis decreased, indicating that the reorientation was suppressed in microgravity. The expression of tubulin genes was suppressed in microgravity. These results suggest that under microgravity conditions, the expression of genes related to microtubule formation was downregulated, which may cause the suppression of microtubule reorientation from transverse to longitudinal directions, thereby stimulating cell elongation in Arabidopsis hypocotyls.
摘要：
太空中的微重力如何影响植物细胞生长是植物细胞生物学和空间生物学的重要问题。我们通过阻力小管空间实验研究了皮质微管在微重力条件下刺激拟南芥（拟南芥）下胚轴伸长生长中的作用。野生型哥伦比亚下胚轴下半部的表皮细胞在微重力下比在轨道上1g长，导致整个下胚轴长度增加。在顶端区域，与外部切向壁相邻的皮质微管主要横向于细胞的长轴，而纵向微管在基底区域占主导地位。在第9至第12个表皮细胞（1至3毫米）从尖端，其中发生了从横向到纵向的微管取向的修改（重新取向），具有横向微管的细胞增加，而那些纵向微管在微重力下减少，相对于横向细胞轴的平均角度减小，表明在微重力下重新定向被抑制。微重力下微管蛋白基因的表达受到抑制。这些结果表明，在微重力条件下，与微管形成相关的基因表达下调，这可能会抑制微管从横向到纵向的重新定向，从而刺激拟南芥下胚轴的细胞伸长。
