ACC-induced apoplast alkalization plays an important role in Arabidopsis cell elongation

The expansion and elongation of plant cells requires the acidification of apoplasts. The acidic growth theory believes that protons as the initial cell wall relaxation factor causes cell expansion. Studies have shown that the low pH of the apoplast increases the activity of expandin in the cell wall, which may break the H + -bound cellulose chain and cross-linked polysaccharide. The pH of apoplast is determined by H + outflow caused by PM H + -ATPase and H + inflow caused by H + binding transporter. Hormone signals such as auxin and environmental factors cause pH changes through PM H + -ATPase and affect cell growth.

In early 2011, Belgian scientist Kris Vissenberg et al. Used non-invasive micro-testing techniques to study the two ends of the Arabidopsis root elongation zone: the transition zone and the posterior meristem zone (approximately 200-450 μm from the root tip). The former stretches slowly, the latter stretches fast, and the adjacent area (from 450 μm to the first root hair area) stretches fast. The study found that the pH value of the tip surface of the transition zone is the highest, and the base of the rapid elongation zone is the lowest. ACC treatment inhibited the rapid elongation of cells, accompanied by alkaloidization of apoplasts. Fusostatin (FC, an activator of PM H + -ATPase) partially reduces cell elongation inhibited by apoplast alkalization, but the inhibitor DCCD (dicyclohexylcarbodiimide) does not reduce The length of the small largest cell. The H + flow rate of the auxin mutant was measured by non-damage micro-testing technology. Finally, it is believed that the effect of ethylene and auxin on PM H + -ATPases activity is a mechanism that affects the ultimate elongation of root cells.

This study proves that ACC plays a role by affecting the auxin content of special cells, and establishes a regulatory model, that is, ACC changes auxin synthesis and transport, resulting in an increase in auxin, and then negatively regulates the activity of H + -ATPase, causing cells Change in elongation.