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Receptor kinase heterodimers refine cambium activity in Arabidopsis

ABSTRACT: In plant development, a receptor kinase may be active in disparate cell types, with each requir-ing different signalling outputs. The ERECTA (ER) receptor kinase and its homologs ERL1 and ERL2 exemplify this pleiotropy. In Arabidopsis, they influence stomatal patterning, shoot meristem function, ovule morphogenesis, xylem fiber differentiation, and cell division in the vascular cambium1–6. Such diverse expression and functionality raise the question of how ER signalling can specify such distinct cell behaviours. One explanation is that cell-type specific interactions with co-receptors, ligands, or other proteins modulate signalling. However, little is known about ER interactors in the vascular cambium, a bifacial stem cell niche that generates phloem and xylem. Combinatorial mutations between ER, ERL1 and ERL2 and receptor kinases of a sec-ond family, PXY, PXL1, and PXL2, show severe cambial defects5,7. Here we discovered that PXY and PXL proteins form heterodimers with ER and ERL2. PXY signalling can be manipulated by altering levels of its cognate ligand, TDIF. In genetic analysis, plant lines in which TDIF levels were altered had dramatic phenotypes that required the presence of ER or ERL2. Our results demonstrate that PXY signalling mediated cambium regulation depends on ER signalling and explains ER function in the cambium. Because the cambium produces xylem, which constitutes the wood in vascular plants, our findings position PXY-ER heterodimers at the centre of the ac-cumulation of this versatile biomaterial and carbon sink.

ORGANISM(S): Arabidopsis thaliana

PROVIDER: GSE263680 | GEO | 2025/11/07

REPOSITORIES: GEO

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Project description:Vascular cambium is a secondary meristem which produces xylem (wood) inwards and phloem (bark) outwards. The activity of cambium leads to expansion in the diameters in plants, that is, secondary growth, and thus contributes to biomass increase. The regulation of cambium development is at multilevel including phytohormones and peptide-receptor kinase (CLE41/44-PXY) signalling pathways. However, only limited progress has been made on the transcriptional regulation level. To construct the transcriptional network that regulates cambium development, we performed a genome wide transcript profiling in sorted procambial and cambial cells in Arabidopsis roots. More than 500 genes were identified as cambium abundant genes via comparison against transcriptomes of other Arabidopsis root cell types. We then investigated the roles of almost all the cambial transcription factors (TFs) and some of their homologous genes during secondary growth. Many of the candidate TFs were highly expressed in cambium based on the promoter GUS fusion and in situ hybridization. An unbiased transcriptional regulatory network was constructed using transcript profiling data collected from inducible overexpression lines for selected candidate TFs and a few major nodes were identified in the network including WOX4 and KNAT1. Moreover, the severity of mutant phenotypes was predicted based on the network. Next, we used the predication as a guide and generated over 70 double mutants within the same or among different TF families to explore the genetic interactions of candidate genes. Phenotype characterization on the secondary growth of the mutants and the overexpression lines identified promoters and inhibitors of cambium activity. The phenotypic data also suggested the redundancy within and among TF families because the phenotypes could be enhanced when additional TFs were mutated. We also found that combinations of certain overexpression lines and mutants led to pronounced increase of cell proliferation or xylem differentiation and in the extreme case the formation of ectopic cambium. We herein propose that cambium development is orchestrated by a wide network at the transcriptional level, where each TF has a different contribution to cell proliferation and differentiation.

Project description:MicroRNAs (miRNAs) are small noncoding regulatory RNAs that play key roles in the process of plant development. To date, extensive studies of miRNAs have been performed in a few model plants, but few efforts have focused on small RNAs in conifers because of the lack of reference sequences for these enormous genomes. In this study, Solexa sequencing of three small RNA libraries obtained from dormant, reactivating, and active vascular cambium in Chinese ﬁr samples identified 76 known miRNAs from 27 miRNA families and 18 new potential miRNAs, of which 15 novel miRNA precursors were validated by RT-PCR and sequencing. More than half of these novel miRNAs displayed stage-specific expression patterns in the vascular cambium. Furthermore, analyzing the 103 miRNAs and their predicted targets indicated that 30% of miRNAs appeared to negatively regulate their targets, of which 4 target genes involved in the regulation of cambial cell division were validated via RNA ligase-mediated rapid amplification of 5’ cDNA ends (RLM 5’-RACE). Interestingly, miRNA156 and miRNA172 may regulate the phase transition in vascular cambium from dormancy to active growth. These results provide new insights into the important regulatory functions of miRNAs in vascular cambium development and wood formation in conifers. The aim of this study is to investigate the small RNA transcriptome in different stages of vascular cambium development in Cunninghamia lanceolata. We herein conducted our comprehensive analysis of a plant sRNAome during development of the vascular cambium in Chinese fir using cryosectioning to isolate cambial meristem, which allowed a higher cellular resolution for defining small RNA profiles and overcomed the limitations resulting from the mixed samples in many previous investigations. Total RNAs of dormant, reactivating, and active cambial meristem, respectively were isolated using the Concert Plant RNA Reagent (Invitrogen, Carlsbad, CA, USA), and were then treated with RNase-free DNase I (Promega, Madison, WI, USA). Twenty micrograms of total RNAs were used and 16 to 30-nt sRNAs were purified using Novex 15% TBE-¬Urea gel (Invitrogen). Two adaptors were sequentially ligated to the 5' and 3' ends of purified sRNAs. The ligation products were further purified from Novex 10% TBE-Urea gel. Reverse transcriptase SuperScript II (Invitrogen) and high-fidelity DNA polymerase Phusion (New England Biolabs, Ipswich, MA, USA) were used in the following RT-PCR reaction. The amplification products were cut from Novex 6% TBE-Urea gel. The purified DNA fragments were used for sequencing on an Illumina 2G Genome Analyzer at the Beijing Genomics Institute, Shenzhen, China.

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Receptor kinase heterodimers refine cambium activity in Arabidopsis

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