Department of Crop and Soil Sciences and Department of Plant and Microbial Biology, North Carolina State University, Raleigh, NC, 27695, USA.
Planta. 2021 Jan 23;253(2):47. doi: 10.1007/s00425-020-03557-1.
Variable cotton fiber diameter is set early in anisotropic elongation by cell-type-specific processes involving the temporal and spatial regulation of microtubules in the apical region. Cotton fibers are single cells that originate from the seed epidermis of Gossypium species. Then, they undergo extreme anisotropic elongation and limited diametric expansion. The details of cellular morphogenesis determine the quality traits that affect fiber uses and value, such as length, strength, and diameter. Lower and more consistent diameter would increase the competitiveness of cotton fiber with synthetic fiber, but we do not know how this trait is controlled. The complexity of the question is indicated by the existence of fibers in two major width classes in the major commercial species: broad and narrow fibers exist in commonly grown G. hirsutum, whereas G. barbadense produces only narrow fiber. To further understand how fiber diameter is controlled, we used ovule cultures, morphology measurements, and microtubule immunofluorescence to observe the effects of microtubule antagonists on fiber morphology, including shape and diameter within 80 µm of the apex. The treatments were applied at either one or two days post-anthesis during different stages of fiber morphogenesis. The results showed that inhibiting the presence and/or dynamic activity of microtubules caused larger diameter tips to form, with greater effects often observed with earlier treatment. The presence and geometry of a microtubule-depleted-zone below the apex were transiently correlated with the apical diameter of the narrow tip types. Similarly, the microtubule antagonists had somewhat different effects between tip types. Overall, the results demonstrate cell-type-specific mechanisms regulating fiber expansion within 80 µm of the apex, with variation in the impact of microtubules between tip types and over developmental time.
异形伸长早期，棉花纤维直径的变化是通过涉及微管在顶端区域的时空调节的细胞类型特异性过程来设定的。棉花纤维是起源于棉属物种种皮的单细胞。然后，它们经历极端的各向异性伸长和有限的直径扩展。细胞形态发生的细节决定了影响纤维用途和价值的质量特性，例如长度、强度和直径。较低且更一致的直径会提高棉花纤维与合成纤维的竞争力，但我们不知道如何控制这种特性。问题的复杂性体现在主要商业种中存在两种主要宽度类别的纤维上：宽纤维和窄纤维存在于普通种植的 Gossypium hirsutum 中，而 Gossypium barbadense 只产生窄纤维。为了进一步了解纤维直径是如何控制的，我们使用胚珠培养、形态测量和微管免疫荧光观察微管拮抗剂对纤维形态的影响，包括在顶端 80µm 内的形状和直径。处理在纤维形态发生的不同阶段在授粉后一天或两天施加。结果表明，抑制微管的存在和/或动态活性会导致形成更大直径的尖端，早期处理的效果通常更大。顶端下方微管耗尽区的存在和几何形状与狭窄尖端类型的顶端直径之间存在短暂相关性。同样，微管拮抗剂在尖端类型之间的影响也略有不同。总体而言，结果表明存在调节纤维在顶端 80µm 内扩展的细胞类型特异性机制，微管对尖端类型和发育时间的影响存在差异。
