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在很大程度上依赖于提供给培养基的生长素。令人惊讶的是，明显缺乏关于载体介导的生长素极性运输基因参与愈伤组织生长调节的信息。在这里，我们深入研究了生长素抗性 1 (AUX1) 流入转运蛋白在愈伤组织生长调节中的作用，比较了光照和黑暗条件下的效果。观察到愈伤组织生长在光照下显着增强。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。在缺乏功能性 AUX1 的aux1-22突变愈伤组织中，IAA 水平大幅降低。尽管如此，与野生型相比，突变愈伤组织表现出明显更高的生长速率。这表明通过 AUX1 依赖性途径减少外源生长素的摄取可能会防止生长限制激素浓度的过度积累。AUX1 缺陷的生长刺激作用被非特异性生长素流入转运抑制剂抵消。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丛的两个最外层细胞层的质膜和邻近气管元件的薄壁组织细胞。值得注意的是，这些位置与生长素浓度最大的区域一致。因此，可以推断 AUX1 介导愈伤组织内生长素的分布。