Mechanical Engineering, University of Colorado Denver, Denver, USA.
Mechanical Engineering, University of Colorado Boulder, Boulder, USA.
Sci Rep. 2021 Feb 11;11(1):3653. doi: 10.1038/s41598-021-83254-5.
The sporangiophores of Phycomyces blakesleeanus have been used as a model system to study sensory transduction, helical growth, and to establish global biophysical equations for expansive growth of walled cells. More recently, local statistical biophysical models of the cell wall are being constructed to better understand the molecular underpinnings of helical growth and its behavior during the many growth responses of the sporangiophores to sensory stimuli. Previous experimental and theoretical findings guide the development of these local models. Future development requires an investigation of explicit and implicit assumptions made in the prior research. Here, experiments are conducted to test three assumptions made in prior research, that (a) elongation rate, (b) rotation rate, and (c) helical growth steepness, R, of the sporangiophore remain constant during the phototropic response (bending toward unilateral light) and the avoidance response (bending away from solid barriers). The experimental results reveal that all three assumptions are incorrect for the phototropic response and probably incorrect for the avoidance response but the results are less conclusive. Generally, the experimental results indicate that the elongation and rotation rates increase during these responses, as does R, indicating that the helical growth steepness become flatter. The implications of these findings on prior research, the "fibril reorientation and slippage" hypothesis, global biophysical equations, and local statistical biophysical models are discussed.
泡囊藻的生孢梗体已被用作研究感觉转导、螺旋生长以及建立细胞壁膨胀生长的全局生物物理方程的模型系统。最近，细胞壁的局部统计生物物理模型正在构建中，以更好地理解螺旋生长的分子基础及其在生孢梗体对感觉刺激的许多生长反应中的行为。以前的实验和理论发现为这些局部模型的发展提供了指导。未来的发展需要调查以前研究中所做的明确和隐含的假设。在这里，进行了实验来检验先前研究中提出的三个假设，即(a)在向光性反应（向单侧光弯曲）和回避反应（远离固体障碍物弯曲）期间，生孢梗体的伸长率、(b)旋转率和(c)螺旋生长陡度 R 保持不变。实验结果表明，所有三个假设对于向光性反应都是不正确的，对于回避反应可能也是不正确的，但结果不太确定。一般来说，实验结果表明，在这些反应中，伸长率和旋转率增加，R 也增加，这表明螺旋生长陡度变得更平坦。这些发现对以前的研究、“原纤维重定向和滑动”假说、全局生物物理方程和局部统计生物物理模型的影响进行了讨论。
