MdBPC2 regulates apple growth

Zhao et al. discovered that MdYUC2a and MdYUC6b are targets of H3K27me3 modification mediated by MdBPC2-MdLHP1, which regulates auxin biosynthesis during apple growth.

Haiyan Zhao, Shuyuan Wan, Yanni Huang, Xiaoqiang Li, Tiantian Jiao, Zhijun Zhang, Baiquan Ma, Lingcheng Zhu, Fengwang Ma, Mingjun Li.

State Key Laboratory for Crop Stress Resistance and High-Efficiency/Shaanxi Key Laboratory of Apple, College of Horticulture, Northwest A&F University, Yangling 712100, Shaanxi, China.

Background: Plant height is an agronomic trait that markedly affects crop yield. It is controlled by the environment, plant hormone metabolism and signaling pathways. Transcription factors play a key role in these processes and have been proposed to be involved in the regulation of plant height. Although little is known about the underlying molecular mechanisms by which they regulate plant dwarfism, a BARLEY B RECOMBINANT/BASIC PENTACYSTEINE (BBR/BPC) transcription factor induces plant dwarfing in Arabidopsis and rice. In apple, the Class I BBR/BPC gene MdBPC2 is highly expressed in dwarfing rootstocks, and MdBPC2-overexpressing plants show a dwarf phenotype. However, the exact mechanism of how BPC transcription factors affect plant structure is not well understood.

Question: What is the role of MdBPC family members in regulating growth and development of apple plants, and how do they function?

Findings: We found that a BBR/BPC transcription factor gene, MdBPC2, was highly expressed in dwarfing rootstocks. When MdBPC2 was overexpressed, auxin content decreased, plant growth was inhibited, plant height decreased, and roots were underdeveloped. These growth defects were reversed by supplementation of exogenous auxin. MdBPC2 bound to the GAGA-Rich element of the MdYUC2a and MdYUC6b promoters, inhibiting their expression. We also found that MdBPC2 interacted with MdLHP1 and recruited it to MdYUC2a and MdYUC6b gene loci to mediate the catalysis and maintenance of H3K27me3 methylation, enhancing chromatin condensation. This process led to the inhibition of MdYUC2a and MdYUC6b transcription, which limited auxin synthesis and ultimately stimulated dwarfism of apple plants.

Next steps: In view of the significant decrease of MdGH3.1 in MdBPC2 overexpressing transgenic plants, we will next focus on the mechanism of MdBPC2 involved in maintaining auxin homeostasis, which will deepen our understanding of how plants promote or inhibit their development in response to environmental changes, thereby enhancing their environmental adaptability.


Haiyan Zhao, Shuyuan Wan, Yanni Huang, Xiaoqiang Li, Tiantian Jiao, Zhijun Zhang, Baiquan Ma, Lingcheng Zhu, Fengwang Ma, Mingjun Li. (2024). The transcription factor MdBPC2 alters apple growth and promotes dwarfing by regulating auxin biosynthesis.