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Grafi, G.

Publications and source records attributed to Grafi, G..

2 recordsLinked to original sources
bioRxiv2018

Epigenetics of floral homeotic genes in relation to sexual dimorphism in the dioecious plant Mercurialis annua

In plants, dioecy characterizes species carrying male and female flowers on separate plants and occurs in about 6% of angiosperms. To date, the molecular mechanism(s) underlying sexual dimorphism is essentially unknown. The ability of gender-reversal by hormone application suggests that epigenetics might play an important role in sexual dimorphism. Proteome analysis of nuclei derived from flower buds of females, males and feminized males of the dioecious plant Mercurialis annua revealed differentially expressed proteins related to nucleic acid binding proteins, hydrolases and transcription factors, including floral homeotic genes. Further analysis showed that class B genes are mainly expressed in male flowers, while class D genes, as well as SUPERMAN-like genes, were mainly expressed in female flowers. Cytokinin-induced feminization of male plants was associated with down-regulation of male-specific genes concomitantly with up-regulation of female-specific genes. No correlation could be found between the expression of class B and D genes and their DNA methylation or chromatin conformation. Thus, our results ruled out epigenetic control over floral identity genes as the major determinants regulating sexual dimorphisms. Rather, determination of sex in M. annua might be controlled upstream of floral identity genes by a gender-specific factor that affects hormonal homeostasis.\n\nHighlightsSex determination in Mercurialis annua is not related to epigenetics of floral homeotic genes but appears to be modulated by an unknown gender-specific regulator(s) that affects hormonal homeostasis.

plant biology↗
bioRxiv2018

CMT3 and SUVH4/KYP silence the exonic retroelement Evelknievel to allow for reconstitution of CMT1 mRNA

Highlights: O_LISilencing of the intragenic Evelknievel (EK) retroelement is maintained by CMT3-KYP/SUVH4 independently of DDM1 and the RdDM pathways.\nC_LIO_LIMethylation and silencing of EK is required for transcription through the EK retroelement.\nC_LIO_LISilencing of EK allows for splicing out of the entire EK and reconstitution of an intact CMT1 mRNA.\nC_LI\n\nBackgroundCHROMOMEHYLASE1 (CMT1) has long been considered a non-essential gene because, in certain Arabidopsis ecotypes, the CMT1 gene is disrupted by the retroelement Evelknievel (EK), inserted within exon 13, or contains frame-shift mutations resulting in a truncated, non-functional protein. Here, we wanted to explore the regulatory pathway responsible for EK silencing in the Ler ecotype and its effect on CMT1 transcription.\n\nResultsMethylome databases confirmed that EK retroelement is heavily methylated but methylation is extended toward CMT1 downstream region. Strong transcriptional activation of EK accompanied by significant reduction in non-CG methylation was found in cmt3 and kyp2, but not in ddm1 or RdDM mutants. EK activation in cmt3 and kyp2 did not interfere with upstream CMT1 expression but abolish transcription through the EK. We identified, in wild type Ler, three spliced variants in which the entire EK is spliced out; one variant (25% of splicing incidents) facilitates proper reconstitution of an intact CMT1 mRNA. We could recover very low amount of the full length CMT1 mRNA from WT Ler and Col but not from cmt3 mutant..\n\nConclusionsOur findings highlight CMT3-SUVH4/KYP as the major pathway silencing the intragenic EK via inducing non-CG methylation. Furthermore, retroelement insertion within exons (e.g., CMT1) may not lead to a complete abolishment of the gene product when the element is kept silent. Rather the element can be spliced out to bring about reconstruction of a very low level of an intact, functional mRNA and possibly to retrieval of an active protein.

plant biology↗