BrRCO promotes leaf lobe formation by repressing BrACP5 expression in Brassica rapa

Abstract

Lobed leaves are advantageous for gas exchange, canopy architecture, and high-density planting; however, the genetic mechanisms of leaf lobe formation in Brassica crops remains poorly understood. Here, lob10.1, our previously identified major QTL controlling the presence/absence of leaf lobes in B. rapa (AA), was fine mapped to a confidence interval of 69.8 kb. REDUCED COMPLEXITY ORGAN (BrRCO, BraA10g032440.3c), a homeodomain leucine zipper class I (HD ZIP I) transcription factor, was predicted to be the most likely candidate gene underlying lob10.1. Null mutations of BrRCO by CRISPR/Cas9 in the lobed-leaf parent RcBr and over-expression in the counter-part near isogenic lines (NIL^RcBr) lead to entire and lobed leaves, respectively. Analysis of the gene evolution revealed that A10. RCO functions as a core gene and was generally negatively selected in B. rapa. Moreover, BrRCO function as a negative regulator by directly binding to promoters of BrACP5 and repressing its expression. The function of ACID PHOSPHATASE TYPE 5 (BrACP5) was subsequently confirmed as VIGS-BrACP5 produced entire leaves in RcBr. This study identified the core gene BrRCO to be involved in the development of leaf lobes in B. rapa and elucidated a new pathway for leaf lobe formation by the BrRCO-BrACP5 module. These findings provide a theoretical basis for the formation of leaf lobes in Brassica crops.

Acknowledgments

We thank Prof. Yaoguang Liu (South China Agriculture University) for kindly providing the sgRNA-Cas9 plant expression vectors. This research was supported by the National Nature Science Foundation of China (31772296 and 31971976) and Hainan Seed Industry Laboratory (B22C49723).

Author Contributions

Conceived and designed the experiments: Y.W., C.F., and J.B. Performed the experiments: Y.S., L.H., J.C.A., L.W., X.W., X.S., W.W., G.Q., and R.J. Wrote the manuscript: Y.S. and J.C.A. Revised the manuscript: J.B., Y.W., C.F., and W.J.W.T. All authors reviewed and approved this submission.

Data availability

The paper contains the data supporting the findings of this study, and supplementary data is available online.

Conflict of interest statement

On behalf of all authors, the corresponding author confirms that there are no conflicts of interest.

Supplementary Data

Supplementary data is available at Horticulture Research online.

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