Expression of polygalacturonases and evidence to support their role during cell separation processes in Arabidopsis thaliana

Abstract

Polygalacturonases (PGs) have been proposed to play an important role in the process of cell separation. The Arabidopsis thaliana genome contains 69 annotated genes that by amino acid homology and transcript organization could be classified as putative PGs and these can be grouped into multiple clades. An analysis of five members located in two separate clades, using reporter fusion constructs and reverse transcription-PCR, revealed that whilst these PGs exhibit high sequence similarity they have distinct patterns of spatial and temporal expression. Sites of expression include the aleurone and endosperm cells surrounding the emerging radicle in a germinating seed, the cortical cells adjacent to the developing lateral root, the abscission zones of floral organs, the dehiscence zone of anthers and siliques, and pollen grains. Silencing of an abscission-related PG (At2g41850), using a T-DNA insertion strategy, delayed the time-course of floral organ loss but did not prevent shedding from taking place. These observations are discussed with regard to the contribution that PGs may play during the life cycle of a plant.

PECTIN METHYLESTERASE48 Is Involved in Arabidopsis Pollen Grain Germination

“…Thus, we can also hypothesize that, upon random action of the PME (PME48 or others from the 13 other pollen-specific PMEs), the partial removal of methylester groups may allow other pectin-degrading enzymes such as PGases and/or PLs to cleave the HG, affecting the rigidity of the cell wall (Micheli, 2001;Sénéchal et al, 2014). In the Arabidopsis genome, 69 annotated genes can be classified as putative PGases (González-Carranza et al, 2007). A semiquantitative RT-PCR analysis investigating 66 among the 69 genes coding for PGases showed that 32 genes were strongly expressed in flower tissues (Kim et al, 2006).…”

cis-Cinnamic Acid Is a Novel, Natural Auxin Efflux Inhibitor That Promotes Lateral Root Formation

“…2C), suggesting active degradation of the pectin-rich middle lamella between adjacent cells. POLYGALACTURONASE ABSCISSION ZONE ARABIDOPSIS THALIANA (PGAZAT)-mediated pectin degradation is known to be important for lateral root outgrowth (González-Carranza et al, 2007;Kumpf et al, 2013), and the PGAZAT promoter turned out to be strongly activated by 10 mM c-CA in cortical and epidermal cell layers surrounding developing lateral roots, but not in the lateral roots themselves (Fig. 2D).…”

“…Arabidopsis ecotype Columbia (Col-0) was used, unless stated elsewhere. Following transgenic lines were in the same ecotype: DII-VENUS, pDR5rev:GFP, pDR5:LUC, pGATA23:GUS, pGAZAT:GUS, pKNOLLE:KNOLLE-GFP, p35S:iaaL, slr, arf7 arf19, and tir1 afb2 afb3 (Romano et al, 1991;Lukowitz et al, 1996;Fukaki et al, 2002;Friml et al, 2003;Dharmasiri et al, 2005;González-Carranza et al, 2007;Okushima et al, 2007;De Rybel et al, 2010;Moreno-Risueno et al, 2010;Brunoud et al, 2012). The transgenic line pCYCB1:GUS was in the ecotype Landsberg erecta (Ler; Colón-Carmona et al, 1999).…”

Regulation of membrane trafficking and organ separation by the NEVERSHED ARF-GAP protein

“…Integral components include a pair of closely related, redundant leucine-rich repeat receptor-like kinases, HAESA (HAE) and HAESA-LIKE2 (HSL2), which are probably activated by the IDA and IDA-LIKE secreted peptides, and which in turn switch on a conserved mitogen-activated protein kinase signal transduction pathway essential for activating the separation process (Butenko et al, 2003;Cho et al, 2008;Jinn et al, 2000;Stenvik et al, 2008). Two of the polygalacturonase enzymes that contribute to the cell wall remodeling required for floral organ shedding have been identified (González-Carranza et al, 2007;Ogawa et al, 2009). Although factors that directly influence abscission zone differentiation have remained elusive, a pair of redundant transcription factors, BLADE-ON-PETIOLE1 (BOP1) and BOP2, is known to affect the patterning of leaf and floral organ proximal zones, a prerequisite for abscission zone specification (Hepworth et al, 2005;McKim et al, 2008;Norberg et al, 2005).…”