A transcriptional repressor HVA regulates vascular bundle formation through auxin transport in Arabidopsis stem

• Published in: The New phytologist Vol. 243; no. 5; pp. 1681 - 1697
• Main Authors: Du, Qian, Yuan, Bingjian, Thapa Chhetri, Gaurav, Wang, Tong, Qi, Liying, Wang, Huanzhong
• Format: Journal Article
• Language: English
• Published: England Wiley Subscription Services, Inc 01.09.2024
• Subjects: Arabidopsis; Arabidopsis - genetics; Arabidopsis - metabolism; Arabidopsis Proteins - genetics; Arabidopsis Proteins - metabolism; Auxins; Biological Transport; Body organs; Cambium - genetics; Cambium - metabolism; cambium activity; CRISPR; Efflux; Epistasis; Epistasis, Genetic; Fluorescence; Gene editing; Gene Expression Regulation, Plant; Gene regulation; Genetic analysis; Genetics; Indoleacetic Acids - metabolism; Lodging; Membrane Transport Proteins - genetics; Membrane Transport Proteins - metabolism; Mutation - genetics; Phenotype; Phenotypes; Pin1 protein; Plant Stems - metabolism; Plant Vascular Bundle - metabolism; Protein Binding; regulation; Regulatory sequences; Repressor Proteins - genetics; Repressor Proteins - metabolism; Transcription activation; transcription factor; Transcription Factors - genetics; Transcription Factors - metabolism; vascular development; VP16 protein; Zinc; Zinc finger proteins; transcription factor; vascular development; regulation; Arabidopsis; cambium activity
• ISSN: 0028-646X; 1469-8137; 1469-8137
• DOI: 10.1111/nph.19970

Summary Vascular bundles transport water and photosynthate to all organs, and increased bundle number contributes to crop lodging resistance. However, the regulation of vascular bundle formation is poorly understood in the Arabidopsis stem. We report a novel semi‐dominant mutant with high vascular activity, hva‐d, showing increased vascular bundle number and enhanced cambium proliferation in the stem. The activation of a C2H2 zinc finger transcription factor, AT5G27880/HVA, is responsible for the hva‐d phenotype. Genetic, biochemical, and fluorescent microscopic analyses were used to dissect the functions of HVA. HVA functions as a repressor and interacts with TOPLESS via the conserved Ethylene‐responsive element binding factor‐associated Amphiphilic Repression motif. In contrast to the HVA activation line, knockout of HVA function with a CRISPR‐Cas9 approach or expression of HVA fused with an activation domain VP16 (HVA‐VP16) resulted in fewer vascular bundles. Further, HVA directly regulates the expression of the auxin transport efflux facilitator PIN1, as a result affecting auxin accumulation. Genetics analysis demonstrated that PIN1 is epistatic to HVA in controlling bundle number. This research identifies HVA as a positive regulator of vascular initiation through negatively modulating auxin transport and sheds new light on the mechanism of bundle formation in the stem.