Arabidopsis ATXR2 deposits H3K36me3 at the promoters of LBD genes to facilitate cellular dedifferentiation

Abstract

Cellular dedifferentiation, the transition of differentiated somatic cells to pluripotent stem cells, ensures developmental plasticity and contributes to wound healing in plants. Wounding induces cells to form a mass of unorganized pluripotent cells called callus at the wound site. Explanted cells can also form callus tissues in vitro. Reversible cellular differentiation-dedifferentiation processes in higher eukaryotes are controlled mainly by chromatin modifications. We demonstrate that ARABIDOPSIS TRITHORAX-RELATED 2 (ATXR2), a histone lysine methyltransferase that promotes the accumulation of histone H3 proteins that are trimethylated on lysine 36 (H3K36me3) during callus formation, promotes early stages of cellular dedifferentiation through activation of () genes. The genes of are activated during cellular dedifferentiation to enhance the formation of callus. Leaf explants from mutants exhibited a reduced ability to form callus and a substantial reduction in gene expression. ATXR2 bound to the promoters of genes and was required for the deposition of H3K36me3 at these promoters. ATXR2 was recruited to promoters by the transcription factors AUXIN RESPONSE FACTOR 7 (ARF7) and ARF19. Leaf explants from double mutants were defective in callus formation and showed reduced H3K36me3 accumulation at promoters. Genetic analysis provided further support that ARF7 and ARF19 were required for the ability of ATXR2 to promote the expression of genes. These observations indicate that the ATXR2-ARF-LBD axis is key for the epigenetic regulation of callus formation in.

The Circadian Clock Sets the Time of DNA Replication Licensing to Regulate Growth in Arabidopsis

“…To generate the mutants, a PCR-based mutagenesis by overlap extension was performed (Lee et al, 2004). The WT and mutated versions of the CDC6 promoter were then cloned into a vector derived from the pCAMBIA1305.1 vector containing the GLUCURONIDASE gene (GUSplus) under the control of a minimal 35S promoter (Lee et al, 2017).…”

JMJ30‐mediated demethylation of H3K9me3 drives tissue identity changes to promote callus formation in Arabidopsis

“…The ARF transcription factors directly bind to the LBD16 and LBD29 promoters and affect LBD expression, consistent with the binding capacity of JMJ30 ( Figure 2c). Moreover, the ARF proteins influence cell fate changes, and accordingly, the arf7-1arf19-2 mutant displays reduction of callus formation (Lee et al, 2017). Therefore, we hypothesized that the ARF transcription factors may recruit JMJ30 and facilitate chromatin modification at associated chromatin regions.…”

“…It has been recently reported that ATXR2 promotes callus formation by stimulating the deposition of H3K36me3 at the LBD16 and LBD29 promoters in developing calli (Lee et al, 2017). Considering that ATXR2 binds the ARF transcription factors and that the JMJ30 and ATXR2 proteins have the same binding capacity to the LBD promoters (Lee et al, 2017), JMJ30 may also work with ATXR2. To test this hypothesis, we examined physical interactions of JMJ30 and ATXR2.…”

“…JMJ30 and ARF transcription factors are functionally coordinated to properly address epigenetic modification at the LBD loci. Moreover, ATXR2 is further recruited, which promotes callus formation through activation of the LBD genes by means of H3K36me3 deposition (Lee et al, 2017). Antagonistic accumulation of two epigenetic marks, H3K9me3 and H3K36me3, is simultaneously regulated at LBD promoters with the help of ARF transcription factors, and the JMJ30 and ATXR2 proteins are indeed interdependent on stable LBD activation and thus callus formation.…”

Histone acetylation orchestrates wound-induced transcriptional activation and cellular reprogramming in Arabidopsis

“…H3K4me3 is typically enriched near the transcription start site and associated with transcriptional initiation, while H3K36me3 is more broadly deposited and associated with transcriptional elongation 38 . Both H3K4me3 and H3K36me3 are linked to various developmental processes and environmental responses 39 and of note, ARABIDOPSIS TRITHORAX-RELATED 2 (ATXR2)mediated H3K36me3 is required for hormone-induced callus formation from Arabidopsis leaf explants 40 . Permissive H3K4me3 and repressive H3K27me3 can co-occur, and this mixed chromatin state is thought to control gene expression during seed development and floral transition 41 .…”