Histone H2B Monoubiquitination is Involved in the Regulation of Cutin and Wax Composition in Arabidopsis thaliana

Abstract

The plant cuticle is a chemically heterogeneous lipophilic layer composed of a cutin polymer matrix and waxes which covers the aerial parts of plants. This layer plays an essential role in the survival of plants by protecting them from desiccation and (a)biotic stresses. Knowledge on the gene networks and mechanisms regulating the synthesis of cuticle components during organ expansion or stress response remains limited however. Here, using five loss-of-function mutants for histone monoubiquitination, we report on the role of two RING E3 ligases, namely HISTONE MONOUBIQUITINATION 1 and 2 (HUB1 and HUB2), in the selective transcriptional activation of four cuticle biosynthesis genes in Arabidopsis thaliana. Microscopy observations showed that in hub1-6 and hub2-2 mutants irregular epidermal cells and disorganized cuticle layers were present in rosette leaves. Water loss measurements on excised rosettes demonstrated that cuticular permeability was significantly increased in the mutants. Chemical analysis of cuticle components revealed that the wax composition was changed and that cutin 16:0 dicarboxylic acid was significantly reduced in all hub mutants. Analysis of transcript levels of selected genes indicated that LACS2, ATT1 and HOTHEAD involved in cutin biosynthesis and CER1 involved in wax biosynthesis were down-regulated in the hub mutants, while the expression of LACERATA, CER3, CER6 and CER10 remained unchanged. Chromatin immunoprecipitation assays further showed that hub mutants are impaired in dynamic changes of histone H2B monoubiquitination at several loci of down-regulated genes. Taken together, these data establish that the regulation of cuticle composition involves chromatin remodeling by H2B monoubiquitination.

Dynamic regulation and function of histone monoubiquitination in plants

“…Precise role of H2Bub1 in plant defense against pathogens still remains largely unclear. Structure defects, e.g., thinner cell walls and altered surface cutin and wax compositions, together with impaired induction of some defense genes might have partly contributed to the increased susceptibility to pathogen infection in the hub mutant plants (Dhawan et al, 2009; Ménard et al, 2014). It is worthy noting that the sdg8 mutants impaired in H3K36me3 deposition also display reduced resistance to necrotrophic fungal pathogen infection (Berr et al, 2010, 2012; Palma et al, 2010).…”

Interactive and noninteractive roles of histone H2B monoubiquitination and H3K36 methylation in the regulation of active gene transcription and control of plant growth and development

“…In Arabidopsis , HISTONE MONOUBIQUITINATION1 (HUB1) and HUB2 act nonredundantly but possibly as a hetero‐tetramer E3, whereas UBIQUITIN CONJUGATING ENZYMES1 (UBC1) and UBC2, but not UBC3, act redundantly as E2 in H2B monoubiquitination (Fleury et al ., ; Liu et al ., ; Cao et al ., ; Xu et al ., ). Characterization of the hub1 , hub2 , hub1hub2 and ubc1ubc2 mutants has revealed that H2Bub1 regulates multiple processes, including cell cycle and plant growth (Fleury et al ., ; Lolas et al ., ), seed dormancy (Liu et al ., ), leaf cuticle formation (Ménard et al ., ), flowering (Cao et al ., ; Gu et al ., ; Xu et al ., ), circadian clock and photomorphogenesis (Bourbousse et al ., ; Himanen et al ., ), as well as plant defense (Dhawan et al ., ; Zou et al ., ). More recent studies have demonstrated that knockdown of HUB1/HUB2 in tomato also affects plant response to pathogens (Zhang et al ., ) and loss of HUB1/HUB2 in rice leads to early heading, dwarfism and anther developmental defects (Cao et al ., ).…”

The cuticle and plant defense to pathogens

“…Highlights of the advances in this area comprise the identification of an ABC transporter ABCG32/PEC1 involved in cuticle assembly (Bessire et al, 2011), the description of several classes of transcription factors involved in cutin and wax biosynthesis (Javelle et al, 2010; Seo et al, 2011; Nadakuduti et al, 2012) or post-transcriptional regulation of cuticle biosynthesis by the zinc-finger protein SERRATE (Voisin et al, 2009). The involvement of protein monoubiquitination in the regulation of cuticle biosynthesis was recently documented as several genes of cutin and wax biosynthetic pathway were found to be targets for histone H2B monoubiquitination (Ménard et al, 2014). …”