GLABROUS INFLORESCENCE STEMS3 binds to and activates RHD2 and RHD4 genes to promote root hair elongation in Arabidopsis.

SUMMARY: Root hairs are crucial in the uptake of essential nutrients and water in plants. This study showed that a zinc finger protein, GIS3 is involved in root hair growth in Arabidopsis. The loss‐of‐function gis3 and GIS3 RNAi transgenic line exhibited a significant reduction in root hairs compared to the wild type. The application of 1‐aminocyclopropane‐1‐carboxylic acid (ACC), an exogenous ethylene precursor, and 6‐benzyl amino purine (BA), a synthetic cytokinin, significantly restored the percentage of hair cells in the epidermis in gis3 and induced GIS3 expression in the wild type. More importantly, molecular and genetic studies revealed that GIS3 acts upstream of ROOT HAIR DEFECTIVE 2 (RHD2) and RHD4 by binding to their promoters. Furthermore, exogenous ACC and BA application significantly induced the expression of RHD2 and RHD4, while root hair phenotype of rhd2‐1, rhd4‐1, and rhd4‐3 was insensitive to ACC and BA treatment. We can therefore conclude that GIS3 modulates root hair development by directly regulating RHD2 and RHD4 expression through ethylene and cytokinin signals in Arabidopsis. Significance Statement: In this paper, we demonstrated that zinc finger protein GIS3 is the key regulator to control root hair development in Arabidopsis. Further experiments demonstrated that GIS3, RHD2, and RHD4 are required for root hair development in response to ethylene and cytokinin signaling. More importantly, the molecular and genetic experiments reveal that GIS3 directly binds to the promoter of RHD2 and RHD4 to regulate root hair elongation in Arabidopsis. These results will provide a novel function of zinc finger protein interacting with hormone signal to control root hair development and a better understanding of the network of zinc finger protein interact with root hair‐related genes to control root hair development in Arabidopsis. [ABSTRACT FROM AUTHOR]