GhMAC3e is involved in plant growth and defense response to Verticillium dahliae.

Key message: GhMAC3e expression was induced by various stresses and hormones. GhMAC3e may regulate plant growth by influencing auxin distribution, and play important roles in Verticillium wilt resistance via mediating SA signaling. The MOS4-Associated Complex (MAC) is a highly conserved protein complex involved in pre-mRNA splicing and spliceosome assembly, which plays a vital role in plant immunity. It comprises key components such as MOS4, CDC5, and PRL1. MAC3A/B, as U-box E3 ubiquitin ligases, are crucial for various plant processes including development, stress responses, and disease resistance. However, their roles in cotton remain largely unknown. In this study, we first cloned the GhMAC3e gene from cotton and explored its biological functions by using virus-induced gene silencing (VIGS) in cotton and transgenic overexpression in Arabidopsis. The results showed that GhMAC3e is ubiquitously expressed in cotton tissues and could be induced by salt stress, Verticillium dahliae (VD) infection, PEG, ABA, ETH, GA3, MeJA, and SA. Silencing GhMAC3e retarded primary stem growth and reduced biomass of cotton coupled with the reduced auxin content in the petioles and veins. Silencing GhMAC3e up-regulated expression of cell growth-related genes GhXTH16 and Gh3.6, while down-regulated GhSAUR12 expression. Ectopic expression of GhMAC3e in Arabidopsis significantly enhanced its resistance to Verticillium wilt (VW) in terms of decreased pathogen biomass and lowered plant mortality. Overexpression of GhMAC3e dramatically upregulated AtPR1 by around 15 fold and more than 262 fold under basal and VD inoculation condition, respectively. This change was not associated with the expression of GhNPR1. In conclusion, GhMAC3e may not only regulate plant growth by influencing auxin distribution and growth-related gene expression, but also play important roles in VW resistance via mediating SA signaling independent of NPR1 transcription level.