Two tomato α‐expansins show distinct spatial and temporal expression patterns during development of nematode‐induced syncytia

Abstract

Cyst nematodes induce specific syncytial feeding structures within the root which develop from an initial cell by successive incorporation of neighbouring cells through local cell wall dissolutions followed by hypertrophy of included cells. Expansins are known to induce cell wall relaxation and extension in acidic pH, and they are involved in many processes requiring wall modification from cell expansion to cell wall disassembly. We studied the expression pattern of tomato (Lycopersicon esculentum L., cv. Money Maker) expansins during development of syncytia induced by the potato cyst nematode (Globodera rostochiensis Woll.). Based on semi-quantitative reverse transcription-polymerase chain reaction, two expansin genes, LeEXPA4 and LeEXPA5, were selected for detailed examinations because their expression was either elevated in infected roots (LeEXPA4) or specifically induced in the root upon nematode infection (LeEXPA5). Both genes have distinct spatial and temporal expression patterns that may reflect their different roles in syncytium development. LeEXPA4 transcripts were localized predominantly in parenchymatous vascular cylinder cells surrounding syncytia. This finding suggests that LeEXPA4 might be involved in cell wall disassembly or relaxation, mediating syncytium expansion and/or development of conductive tissues. By contrast, LeEXPA5 transcripts were localized in enlarging syncytial elements. Similarly, in immunogold localization experiments, polyclonal antibodies localized the LeEXPA5 protein in cell walls of syncytial elements. This expression pattern suggests that LeEXPA5 gene is specifically involved in enlargement of cells incorporated into syncytium.

Immunolocalization of α-Expansin Protein (NtEXPA5) in Tobacco Roots in the Presence of the Arbuscular Mycorrhizal Fungus Glomus Mosseae Nicol. & Gerd

“…Expansins are ~27 kDa and ~225 aa proteins consisting of two compact domains: the N-terminal, which resembles the catalytic domain of family 45 glycoside hydrolases (GH45); and the C-terminal, which has been reported as a cellulose-binding domain (Yennawar et al, 2006). Expansin genes appear to be highly conserved throughout plant evolution, but proteins remarkably similar to plant expansin sequences have also been found in Dictyostelium discoideum, (Li et al, 2002), nematodes (Qin et al, 2004;Kudla et al, 2005;Fudali et al, 2008), the ascomycete fungi Trichoderma reesii (Saloheimo et al, 1994), mussels (Xu et al, 2001) and the bacterium Bacillus subtilis (Kerff et al, 2008). The expansin-like sequences in bacteria, animals and fungi appear to be restricted to organisms involved in plant pathogenesis or plant cell wall digestion (Li et al, 2002).…”

The Regulation of Cell Wall Extensibility during Shade Avoidance: A Study Using Two Contrasting Ecotypes of Stellaria longipes

“…However, some studies also suggest that the correlation between expansin activity and growth does not always hold (Caderas et al, 2000;Reidy et al, 2001). Expansins are strongly regulated during plant responses to environmental stresses, such as drought (Jones and McQueen-Mason, 2004;Zhu et al, 2007), flooding (Cho and Kende, 1997;Colmer et al, 2004;Vreeburg et al, 2005), and response to pathogens (Ding et al, 2008;Fudali et al, 2008).…”

RhNAC2 and RhEXPA4 Are Involved in the Regulation of Dehydration Tolerance during the Expansion of Rose Petals

“…Expansins are strongly regulated at the transcriptional level by WDS in maize (Zea mays; Wu et al, 2001;Zhu et al, 2007) and in a resurrection plant, Craterostigma plantagineum (Jones and McQueen-Mason, 2004). Heat tolerance, shade stress, low oxygen, and pathogens also up-regulate the expression of expansins in plants (Colmer et al, 2004;Xu et al, 2007;Ding et al, 2008;Fudali et al, 2008;Sasidharan et al, 2008). Overexpression of TaEXPB23, a wheat expansin gene, improves drought tolerance in tobacco (Nicotiana tabacum; .…”