Comparative transcriptome analysis of salt tolerance of roots in diploid and autotetraploid citrus rootstock (C. junos cv. Ziyang xiangcheng) and identification of salt tolerance-related genes

Abstract

Polyploidization is a widespread phenomenon in flowering plants, and it often enhances abiotic stress tolerance. However, the related molecular mechanism remains largely unknown, especially for perennial woody plants. Here, we found that autotetraploid citrus (Citrus junos Sieb. ex Tanaka) had greater salt tolerance than their diploid progenitors. Transcriptome analysis identified a large number of differentially expressed genes (DEGs) between autotetraploid and diploid roots under salt stress. GO analysis showed that chitin response-related genes were enriched in roots of autotetraploid. Consistently, the autotetraploids exhibited higher chitinases activity than the diploids under salt stress. The top five transcription factor (TF) families with the largest number of TFs were bHLH, ERF, MYB, NAC, and WRKY in autotetraploids and diploids, and 25 TFs were higher expressed in autotetraploids than in diploids under salt stress. Our results revealed that salt stress induced the activation of chitin pathway, thus reducing in ROS accumulation, eventually enhancing salt tolerance of autotetraploid citrus. Our research provides the theoretical basis for citrus breeding aiming at abiotic stress tolerance enhancement.