CsMYB15 positively regulates Cs4CL2-mediated lignin biosynthesis during juice sac granulation in navel orange

Fang Song; Zixuan Li; Ce Wang; Yingchun Jiang; Zhijing Wang; Ligang He; Xiaofang Ma; Yu Zhang; Xin Song; Jihong Liu; Liming Wu

doi:10.3389/fpls.2023.1223820

CsMYB15 positively regulates Cs4CL2-mediated lignin biosynthesis during juice sac granulation in navel orange

Front Plant Sci. 2023 Jun 30:14:1223820. doi: 10.3389/fpls.2023.1223820. eCollection 2023.

Authors

Fang Song^{1

2}, Zixuan Li¹, Ce Wang¹, Yingchun Jiang^{1

2}, Zhijing Wang¹, Ligang He¹, Xiaofang Ma¹, Yu Zhang¹, Xin Song¹, Jihong Liu^{2

3}, Liming Wu^{1

2}

Affiliations

¹ Hubei Key Laboratory of Germplasm Innovation and Utilization of Fruit Trees, Institute of Fruit and Tea, Hubei Academy of Agricultural Science, Wuhan, China.
² Hubei Hongshan Laboratory, Wuhan, China.
³ College of Horticulture and Forestry Sciences, Huazhong Agricultural University, Wuhan, China.

Abstract

'Lane Late', a late-maturing navel orange cultivar, is mainly distributed in the Three Gorges Reservoir area, which matures in the late March of the next year and needs overwintering cultivation. Citrus fruit granulation is a physiological disorder, which is characterized by lignification and dehydration of juice sac cells, seriously affecting the commercial value of citrus fruits. The pre-harvest granulation of late-maturing navel orange is main caused by low temperature in the winter, but its mechanism and regulation pattern remain unclear. In this study, a SG2-type R2R3-MYB transcription factor, CsMYB15, was identified from Citrus sinensis, which was significantly induced by both juice sac granulation and low temperature treatment. Subcellular localization analysis and transcriptional activation assay revealed that CsMYB15 protein was localized to the nucleus, and it exhibited transcriptional activation activity in yeast. Over-expression of CsMYB15 by stable transformation in navel orange calli and transient transformation in kumquat fruits and navel orange juice sacs significantly increased lignin content in the transgenic lines. Further, Yeast one hybrid, EMSA, and LUC assays demonstrated that CsMYB15 directly bound to the Cs4CL2 promoter and activated its expression, thereby causing a high accumulation of lignin in citrus. Taken together, these results elucidated the biological function of CsMYB15 in regulating Cs4CL2-mediated lignin biosynthesis, and provided novel insight into the transcriptional regulation mechanism underlying the juice sac granulation of late-maturing navel orange.

Keywords: CsMYB15; granulation; lignin biosynthesis; transcription factor; ‘Lane late’ navel orange.

Grants and funding

This research was funded by National Natural Science Foundation of China (32102309), Hubei Provincial Academy of Agricultural Sciences Youth Top Talent Training Program and Hubei Provincial Agricultural Science and Technology Innovation Fund (2019-620-000-001-023). Sincere gratitude goes to Professor Ping Liu from Huazhong Agriculture University, Wuhan, China for her English editing and language polishing of this manuscript.