Differential gene expression in nematode‐induced feeding structures of transgenic plants harbouring promoter—gusA fusion constructs

Abstract

Sedentary plant-parasitic nematodes are able to induce specialized feeding structures in the root system of their host plants by triggering a series of dramatic cellular responses. These changes presumably are accompanied by a reprogramming of gene expression. To monitor such changes, a variety of promoter-gusA fusion constructs were introduced into Arabidopsis and tobacco. Transgenic plants were analysed histochemically for GUS activity in the nematode feeding structures after infection with either Heterodera schachtii or Meloidogyne incognita. Promoters of the Cauliflower Mosaic Virus 35S gene, the bacterial nopaline synthase, rooting loci (rol) and T-cyt genes and the plant-derived phenylalanine ammonia-lyase I gene, which are highly active in non-infected roots, were all downregulated in the feeding structures as indicated by the strong decrease of GUS activity inside these structures. Less stringent downregulation was observed with chimeric gusA fusion constructs harbouring truncated rolB and rolC promoter sequences. Similar observations were made with transgenic Arabidopsis lines that carried randomly integrated promoterless gusA constructs to identify regulatory sequences in the plant genome. Most of the lines that were selected for expression in the root vascular cylinder demonstrated local downregulation in feeding structures after infection with H. schachtii. The reverse pattern of GUS activity, a blue feeding structure amidst unstained root cells, was also found in several lines. However, GUS activity that was entirely specific for the feeding structures was not observed. Our data show that the expression of a large number of genes is influenced during the development of the nematode feeding structures.

Nematode Pathogenesis and Resistance in Plants

“…In a complementary approach, transformation of plants with "promoter traps" by random integration of promoterless GUS constructs has identified regions of the genome in which expression of GUS is increased or decreased upon nematode infection (Goddijn et al, 1993;Gheysen et al, 1996). Transgenic plants with a variety of tissue specificities and differences in timing of GUSexpression have been identified in Arabidopsis.…”

“…Many genes are downregulated in giant cells or developing galls as well as systemically in the plant after nematode infection (Hammond-Kosack et al, 1989;Goddijn et al, 1993). The powerful cauliflower mosaic virus 35s promoter has been reported to be silenced in developing galls within days after root-knot nematode infection (Goddijn et al, 1993).…”

“…The thin, transparent roots have permitted video microscopy studies that have greatly enhanced our understanding of nematode behavior inside roots. Furthermore, a large array of transgenic Arabidopsis lines containing reporter gene constructs whose expression is modulated by nematode infection has already been generated (Goddijn et al, 1993;Gheysen et al, 1996). Analysis of theselines should produce information on the timing and sequence of events during the plant's response to nematode infection.…”

Auxin-Sensitive Elements from Promoters of Tobacco GST Genes and a Consensus as-1-Like Element Differ Only in Relative Strength

“…Chimeric GUS genes present in the plasmids YEasl03, YEasll4, Yeascon, YE55, and YE283 were gel purified after digestion with EcoRI and cloned into the wide host range vector pMOG22 (Goddijn et al, 1993). Clones with the remaining 950 bp of the A fragment (EcoRI site at 26104 within fragment 25157-7479 of phage A) adjacent to the right border were selected.…”

Nematode Infection Triggers the de Novo Formation of Unloading Phloem That Allows Macromolecular Trafficking of Green Fluorescent Protein into Syncytia

“…These changes in gene expression could not, however, clearly be assigned to the syncytium but rather to the root zone containing this nematode-induced structure. In contrast, analyses of transgenic Arabidopsis plants harboring promoter-reporter gene constructs revealed changes in the activities of various genes within the syncytia (Goddijn et al, 1993;Niebel et al, 1996;Barthels et al, 1997;de Almeida Engler et al, 1999;Puzio et al, 2000;Jü rgensen et al, 2003;Thurau et al, 2003). Among these genes are a Gln-rich domain protein, cyclin-dependent kinases, mitotic cyclins, and a disaccharide transporter (Niebel et al, 1996;de Almeida Engler et al, 1999;Puzio et al, 2000;Jü rgensen et al, 2003).…”