The Arabidopsis mutant cev1 links cell wall signaling to jasmonate and ethylene responses

Abstract

Biotic and abiotic stresses stimulate the synthesis of jasmonates and ethylene, which, in turn, induce the expression of genes involved in stress response and enhance defense responses. The cev1 mutant has constitutive expression of stress response genes and has enhanced resistance to fungal pathogens. Here, we show that cev1 plants have increased production of jasmonate and ethylene and that its phenotype is suppressed by mutations that interrupt jasmonate and ethylene signaling. Genetic mapping, complementation analysis, and sequence analysis revealed that CEV1 is the cellulose synthase CeSA3. CEV1 was expressed predominantly in root tissues, and cev1 roots contained less cellulose than wild-type roots. Significantly, the cev1 mutant phenotype could be reproduced by treating wild-type plants with cellulose biosynthesis inhibitors, and the cellulose synthase mutant rsw1 also had constitutive expression of VSP. We propose that the cell wall can signal stress responses in plants.

Figure 1.

The cev1 Mutant Constitutively Produces JA. Four-week-old plants were assayed for JA, its intermediate 12-oxo-phytodienoic acid (OPDA), and the 16:3 fatty acid derivative dinor-12-oxo-phytodienoic acid (dnOPDA).

Figure 2.

The Ethylene Receptor ETR1 Is Required for Shortened Hypocotyls in the cev1 Mutant. (A) Seedlings grown in the dark for 4 days on Murashige and Skoog (1962) (MS) agar. (B) Lengths of hypocotyls of dark-grown seedlings. T-bars indicate sd values for 10 seedlings.

Figure 3.

ETR1 and COI1 Are Partially Required for Root Growth Inhibition in the cev1 Mutant. (A) Eight-day-old seedlings grown on MS agar. (B) Root lengths of 12-day-old seedlings grown on MS agar. T-bars indicate sd values for 10 roots.

Figure 4.

Complementation Analysis of cev1. (A) Partial restriction endonuclease map of the K2A11 TAC clone and DNA fragments used in complementation analysis of cev1. Arrows indicate putative open reading frames. The DNA fragment SB6.6 complemented the cev1 phenotype. (B) Photographs of 4-week-old wild-type, cev1, and SB6.6 plants. (C) Scheme of the predicted CEV1 protein showing the cellulose synthase signature motif D,D,D,QXXRW and the position of the cev1 mutation.

Figure 5.

Expression Pattern of the CEV1 Gene. (A) Total RNA was extracted, and 1 μg was electrophoresed, blotted, and probed for CEV1 or 18S mRNA. (B) to (E) Histochemical assays of GUS activity in CEV1::GUS transgenic plants. (B) Rosette of a 2-week-old seedling. (C) Roots of 2-week-old seedlings. (D) Flower. (E) Three-day-old dark-grown seedling.

Figure 6.

Cellulose Biosynthesis Inhibitors Induce COI1-Dependent JA Responses. (A) and (B) Seedlings were grown on MS agar for 12 days, transplanted onto MS agar supplemented with 20 μM MeJA, 5 μM IXB, or 5 μM DCB, and incubated for another 3 days. (A) Seedlings of wild-type, cev1, and coi1-1 plants. (B) Total RNA was extracted, and 1 μg was electrophoresed, blotted, and probed for VSP or PDF1.2 mRNA. (C) Seedlings were germinated for 5 days on MS agar at 22°C and transferred to 30°C for another 7 days. Total RNA was extracted, and 1 μg was electrophoresed, blotted, and probed for VSP mRNA.

Figure 7.

Time Course of the Induction of VSP Expression by Cellulose Biosynthesis Inhibitors. (A) VSP1::LUC activity. (B) VSP2::LUC activity. Seedlings were grown on MS agar for 12 days and transplanted onto MS agar supplemented with 20 μM MeJA, 5 μM IXB, or 5 μM DCB. LUC activity was measured at the times indicated using low-light images of plants taken with a liquid nitrogen–cooled charge-coupled device imaging system. T-bars indicate sd values for eight seedlings. Circles, control; squares, MeJA; triangles, IXB; inverted triangles, DCB.