miR171-targeted SCARECROW-LIKE genes CsSCL2 and CsSCL3 regulate somatic embryogenesis in citrus

• Published in: Plant physiology (Bethesda) Vol. 192; no. 4; pp. 2838 - 2854
• Main Authors: Feng, Meng-Qi, Jiang, Nan, Wang, Peng-Bo, Liu, Yue, Xia, Qiang-Ming, Jia, Hui-Hui, Shi, Qiao-Fang, Long, Jian-Mei, Xiao, Gong-Ao, Yin, Zhao-Ping, Xie, Kai-Dong, Guo, Wen-Wu, Wu, Xiao-Meng
• Format: Journal Article
• Language: English
• Published: US Oxford University Press 03.08.2023
• Subjects: Biotechnology; Citrus - genetics; Citrus - metabolism; Gene Expression Regulation, Plant; Plant Somatic Embryogenesis Techniques; Reactive Oxygen Species - metabolism; Regeneration; RNA-Seq
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1093/plphys/kiad289

Abstract Somatic embryogenesis (SE) is a key regeneration pathway in various biotechnology approaches to crop improvement, especially for economically important perennial woody crops like citrus. However, maintenance of SE capability has long been a challenge and becomes a bottleneck in biotechnology-facilitated plant improvement. In the embryogenic callus (EC) of citrus, we identified 2 csi-miR171c–targeted SCARECROW-LIKE genes CsSCL2 and CsSCL3 (CsSCL2/3), which exert positive feedback regulation on csi-miR171c expression. Suppression of CsSCL2 expression by RNA interference (RNAi) enhanced SE in citrus callus. A thioredoxin superfamily protein CsClot was identified as an interactive protein of CsSCL2/3. Overexpression of CsClot disturbed reactive oxygen species (ROS) homeostasis in EC and enhanced SE. Chromatin immunoprecipitation sequencing (ChIP-Seq) and RNA-Seq identified 660 genes directly suppressed by CsSCL2 that were enriched in biological processes including development-related processes, auxin signaling pathway, and cell wall organization. CsSCL2/3 bound to the promoters of regeneration-related genes, such as WUSCHEL-RELATED HOMEOBOX 2 (CsWOX2), CsWOX13, and Lateral Organ Boundaries Domain 40 (LBD40), and repressed their expression. Overall, CsSCL2/3 modulate ROS homeostasis through the interactive protein CsClot and directly suppress the expression of regeneration-related genes, thus regulating SE in citrus. We uncovered a regulatory pathway of miR171c-targeted CsSCL2/3 in SE, which shed light on the mechanism of SE and regeneration capability maintenance in citrus. The SCARECROW-LIKE transcription factors affect embryo formation from citrus calluses possibly through the interactive thioredoxin protein and regeneration-related genes.