Plant Physiology and Biotechnology Department, Nicolaus Copernicus University in Toruń, Lwowska 1, 87-100 Toruń, Poland; Centre for Modern Interdisciplinary Technologies, Nicolaus Copernicus University in Toruń, Wileńska 4, 87-100 Toruń, Poland.
Plant Physiology and Biotechnology Department, Nicolaus Copernicus University in Toruń, Lwowska 1, 87-100 Toruń, Poland.
J Plant Physiol. 2024 Feb;293:154168. doi: 10.1016/j.jplph.2023.154168. Epub 2024 Jan 1.
Callus sustained growth relies heavily on auxin, which is supplied to the culture medium. Surprisingly, there is a noticeable absence of information regarding the involvement of carrier-mediated auxin polar transport gene in callus growth regulation. Here, we delve into the role of the AUXIN RESISTANT 1 (AUX1) influx transporter in the regulation of callus growth, comparing the effects under conditions of light versus darkness. It was observed that callus growth was significantly enhanced under light illumination. This growth-stimulatory effect was accompanied by a decrease in the levels of free auxin within the callus cells when compared to conditions of darkness. In the aux1-22 mutant callus, which lacks functional AUX1, there was a substantial reduction in IAA levels. Nonetheless, the mutant callus exhibited markedly higher growth rates compared to the wild type. This suggests that the reduction in exogenous auxin uptake through the AUX1-dependent pathway may prevent the overaccumulation of growth-restricting hormone concentrations. The growth-stimulatory effect of AUX1 deficiency was counteracted by nonspecific auxin influx transport inhibitors. This finding shows that other auxin influx carriers likely play a role in facilitating the diffusion of auxin from the culture medium to sustain high growth rates. AUX1 was primarily localized in the plasma membranes of the two outermost cell layers of the callus clump and the parenchyma cells adjacent to tracheary elements. Significantly, these locations coincided with the regions of maximal auxin concentration. Consequently, it can be inferred that AUX1 mediates the auxin distribution within the callus.
愈伤组织的持续生长很大程度上依赖于生长素，它被供应到培养基中。令人惊讶的是，关于载体介导的生长素极性运输基因在愈伤组织生长调控中的参与，几乎没有相关信息。在这里，我们研究了生长素不敏感 1（AUX1）流入转运体在调节愈伤组织生长中的作用，比较了光照和黑暗条件下的效果。结果观察到，在光照下愈伤组织的生长明显增强。与黑暗条件相比，这种生长刺激作用伴随着愈伤组织细胞内游离生长素水平的降低。在 aux1-22 突变体愈伤组织中，缺乏功能的 AUX1，IAA 水平显著降低。然而，突变体愈伤组织的生长速率明显高于野生型。这表明通过 AUX1 依赖途径减少外源性生长素的摄取可能防止生长限制激素浓度的过度积累。AUX1 缺乏的生长刺激作用被非特异性生长素流入转运抑制剂所抵消。这一发现表明，其他生长素流入载体可能在促进生长素从培养基中的扩散以维持高生长速率方面发挥作用。AUX1 主要定位于愈伤组织团块的最外层两层细胞的质膜和与导管元件相邻的薄壁细胞中。重要的是，这些位置与生长素浓度最大的区域相吻合。因此，可以推断 AUX1 介导了愈伤组织内生长素的分布。
