Gossypium hirsutum Salt Tolerance Is Enhanced by Overexpression of G. arboreum JAZ1

Abstract

<i>Gossypium arboreum</i> possesses many favorable traits including robust defense against biotic and abiotic stress although it has been withdrawn from the market because of lower yield and fiber quality compared to <i>G. hirsutum</i> (upland cotton). It is therefore important to explore and utilize the beneficial genes of <i>G. arboretum</i> for <i>G. hirsutum</i> cultivar breeding. Here, the function of <i>G. arboreum JAZ1</i> in tolerance to salt stress was determined through loss-of-function analysis. GaJAZ1can interact with GaMYC2 to repress expression of downstream genes whose promoters contain a G-box <i>cis</i> element, affecting plant tolerance to salinity stress. The experimental data from NaCl treatments and a 2 year continuous field trial with natural saline-alkaline soil showed that the ectopically overexpressed <i>GaJAZ1</i> significantly increased salt tolerance in upland cotton compared to the wild type, showing higher growth vigor with taller plants, increased fresh weight, and more bolls, which is due to reprogrammed expression of tolerance-related genes and promotion of root development. High-throughput RNA sequencing of <i>GaJAZ1</i> transgenic and wild-type plants showed many differentially expressed genes involved in JA signaling and biosynthesis, salt stress-related genes, and hormone-related genes, suggesting that overexpressing <i>GaJAZ1</i> can reprogram the expression of defense-related genes in <i>G. hirsutum</i> plants to increase tolerance to salt stress. The research provides a foundation to explore and utilize favorable genes from <i>Gossypium</i> species for upland cotton cultivar breeding.