Cove D J, Quatrano R S, Hartmann E
Department of Genetics, University of Leeds, UK.
Development. 1996 Jan;122(1):371-9. doi: 10.1242/dev.122.1.371.
Ceratodon protoplasts regenerate by polar outgrowth to form cell filaments. The kinetics of regeneration show that some cellular event has to be completed before regeneration can be initiated. The development of the regeneration axis is strongly influenced by light, with axis alignment and axis polarity being fixed independently. We define axis alignment as the relationship of the regeneration axis to the incident light, independent of polarity. Thus protoplasts regenerating directly towards, or directly away from the light source are defined as being similarly aligned but with opposite polarity. Protoplasts that regenerate in unidirectional red light form axes that are aligned parallel to the light direction, with about 70% being polarised towards the light and about 30% away. In unidirectional blue or white light, almost all protoplasts regenerate towards the light but axis alignment is determined less stringently. Re-orientation of protoplasts regenerating in unidirectional light shows that axis alignment is fixed between 8 and 9 hours before protoplasts regenerate and that axis polarity is fixed later. When protoplasts are removed from directional light to either non-directional light or to darkness, regeneration axes continue to be aligned by the earlier directional stimulus for at least 24 hours. Thus although axis alignment is fixed only about 8 hours before regeneration, in the absence of contradictory information about directionality in the light environment, protoplasts retain a memory of light direction for much longer. However, both reorientation and removal from a directional light field have profound effects on axis polarity; the pattern observed in undisturbed protoplasts being lost. To account for these observations, we propose that separate gradients are established independently to determine the alignment and polarity of the regeneration axis respectively. The alignment gradient is established rapidly and is steeper in red than in blue or white light, the polarity gradient is established slowly and is steeper in white or blue light than in red. These studies will now allow a genetic dissection of these processes in moss.
角齿藓原生质体通过极性生长再生形成细胞丝。再生动力学表明，在再生开始之前，某些细胞事件必须完成。再生轴的发育受到光的强烈影响，轴的排列和轴的极性是独立确定的。我们将轴的排列定义为再生轴与入射光的关系，与极性无关。因此，直接朝向或远离光源再生的原生质体被定义为排列相似但极性相反。在单向红光中再生的原生质体形成与光方向平行排列的轴，约70%的原生质体向光极化，约30%背光极化。在单向蓝光或白光中，几乎所有原生质体都向光再生，但轴的排列确定得不太严格。在单向光中再生的原生质体重新定向表明，轴的排列在原生质体再生前8至9小时固定，轴的极性稍后固定。当原生质体从定向光转移到非定向光或黑暗中时，再生轴至少在24小时内继续由早期的定向刺激排列。因此，尽管轴的排列在再生前约8小时才固定，但在光环境中没有关于方向性的矛盾信息时，原生质体对光方向的记忆会保留更长时间。然而，重新定向和从定向光场中移除都对轴的极性有深远影响；在未受干扰的原生质体中观察到的模式消失了。为了解释这些观察结果，我们提出分别独立建立梯度来分别确定再生轴的排列和极性。排列梯度建立迅速，在红光中比在蓝光或白光中更陡，极性梯度建立缓慢，在白光或蓝光中比在红光中更陡。这些研究现在将允许对苔藓中的这些过程进行遗传学剖析。
