小背景: In Arabidopsis roots, SHORT‐ROOT (SHR) functions to promote periclinal division in cortex/endodermis initials which generates the ground tissue patterning.

提出问题: Despite multiple downstream transcription factors and interplaying hormone pathways have been reported, the cellular mechanism that affects SHR mediated periclinal division is still largely unclear. 

主要发现：Here, we found that SHR could substantially elevate reactive oxygen species (ROS) level in Arabidopsis roots by activating respiratory burst oxidase homologues (RBOHs).

结果-H2O2：Among the ROS products, hydrogen peroxide (H2O2) rather than superoxide (O2‐) played a critical role in SHR mediated periclinal division. Scavenging H2O2 could markedly impair SHR ability to induce periclinal division.

结果-SA：We also revealed that salicylic acid (SA) could promote H2O2 level via repressing CAT expression, which greatly increased periclinal division in root endodermis. As a result, middle cortex was more frequently formed in the endodermis of snc1, a mutant with accumulated endogenous SA and H2O2.

结果-SHR-SA-ROS：In addition to RBOHs, SHR also activated SA pathway, which might contribute to the elevated H2O2 level induced by SHR.

结论：Thus, our data suggest a mechanism by which SHR creates the optimal micro‐environment for periclinal division by maintaining ROS homeostasis in Arabidopsis roots.