Molecular details of tomato extensin and glycine-rich protein gene expression

Abstract

In a recent publication (Plant Molecular Biology 16: 547-565 (1991)), Showalter et al. described the isolation and initial characterization of fifteen extensin and extensin-like tomato cDNAs. These cDNAs were determined to fall into five distinct classes; class I and II clones encoded extensins, class III and V clones encoded glycine-rich proteins (GRPs), and class IV clones encoded a portion of a GRP sequence on one DNA strand and a portion of an extensin sequence on the other DNA strand. In this publication, a more detailed analysis of the expression of these cDNA classes was performed with respect to wounding in various tomato organs, development, kinetics and systemic extent of the wound response, ethylene treatment, abscisic acid (ABA) treatment, and drought stress by using RNA gel blot hybridizations. In general, extensin gene expression was readily detected in stems and roots, but not in leaves. With both class I and II extensin cDNA probes, wound-induced accumulation of mRNA in stems was first detected between 4 and 8 h after wounding with maximal accumulation occurring after 12 h. Moreover, these extensin wound responses were detected locally at the wound site but not systemically. Expression of the class III GRP was largely limited to wounded stem tissue. Initial detection and maximal accumulation of the class III GRP mRNA was similar to the extensins mRNAs; however, this GRP wound response occurred both locally and systemically. Additionally, abscisic acid treatment and drought stress resulted in the marked accumulation of the class III GRP mRNA in tomato stems, but did not alter the expression of the other cDNA classes. In contrast, expression of the class V GRP occurred in stems and roots and to a lesser extent in leaves and decreased in response to wounding over a 24 h time period. The class V GRP wound response was further characterized by an early, transient accumulation of mRNA occurring 2-4 h after wounding in stems and by its local nature.

A gene for Brassica napus extensin is differentially expressed on wounding

“…These results confirm that ethylene is involved in the wound-regulated expression of the extA gene. The involvement of ethylene in extensin gene expression has been observed before; Showalter et al [19] showed that exposure of tomato plants to ethylene for 24 h in enclosed containers resulted in the accumulation of class 1 and class 2 extensin transcripts. As ethylene is involved in plant senescence, we suppose that the old senescent leaves (Fig.…”

“…This contrasts with the results obtained by Showalter etal. [19] on the pattern of tomato extensin m R N A accumulation at and adjacent to the wound site, where expression of the Class 1 and Class 11 tomato extensins was primarily restricted to the wounded, cut ends. However, in the same study, the Class 111 tomato G R P transcripts accumulated at the cut ends and in the middle sections, showing a localised as well as a systemic response.…”

“…Increases in the levels of extensin transcripts as a result of wounding have been seen in many other systems. In carrot, [23], two transcripts of 1.5 and 1.8 kb accumulate differentially as a result of wounding; in bean [3], excision wounding of hypocotyls leads to the strong induction of a 3.6 kb transcript within 1.5 h; in tomato [ 19], the Class 1 and Class 2 extensins are locally accumulated after wounding; in tobacco leaf, which normally contains very low levels of extensin mRNA, induction is observed upon wounding [13]; in soybean, the proline-rich protein gene Prp 2 which is not normally expressed in leaf is induced by wounding [24]. The results presented here therefore complement and confirm earlier work on wound induced alterations of extensin gene expression, especially the studies performed by Showalter et al [ 19] on the woundinduced extensin genes of tomato.…”

Structure and Function of Plant Cell Wall Proteins

“…As shown in Table 3, dicot GRPs, like extensin, are expressed in response to a variety of developmental and stress conditions (Condit and Meagher, 1987;Keller et al, 1988;van Kan et al, 1988;de Oliveira et al, 1990;Linthorst et al, 1990;Showalter et al, 1991Showalter et al, , 1992. Monocot GRPs are likewise expressed in response to a similar set of conditions (Gómez et al, 1988;Mundy and Chua, 1988;Lei and Wu, 1991;Didierjean et al, 1992).…”

Ozone induction of extensin mRNA in Scots pine, Norway spruce and European beech

“…The 0-75 kb band was almost indetectable 8 h after fumigation was ended (Eig, 1). A rapid increase in extensin transcript accumulation also has been shown in tomato stems and bean hypocotyl tissue upon wounding (Corbin et al, 1987;Showalter e« a/., 1992;Sauer et al, 1990), The rapid accumulation of extensin niRNAs is similar to the ozone induction of ^-1,3-glucanase mRNA in tobacco , as v^'ell as to the crossinduction of defensive genes in parsley (EckeyKaltenbach et al, 1994), The strong increase in extensin mRNA in ozone-treated pine needles contrasted with the response of wounded tomato leaves, for which no extensin mRNA accumulation is found (Showalter & Varner, 1987;Showalter et al, 1992), However, in tobacco leaves strong accumulation of wound-induced extensin mRNA is found, which is probably mediated by woundinduced ethylene formation (Memelink et al, 1993), Since exposure to ozone results in a rapid ethylene formation in other plant species (Tingey, Standley & Eield, 1976;Langebartels et al, 1991), it is possible that this also occurred in needles of Scots pine seedlings, so that a rapid and strong increase in extensin mRNA was mediated via this hormone.…”