RNA expression patterns of a type 2 metallothionein-like gene from rice

Abstract

A type 2 metallothionein-like gene from rice, OsMT-2 (Oryza sativa metallothionein-like gene-2), was isolated in its cDNA form and sequenced. By northern analyses OsMT-2 expression was shown to be induced under stress by sucrose starvation, heat shock and, to a lesser extent, abscisic acid, but not excess metals, including copper. Its response to sucrose starvation was transient and different from OsMT-1, a type 1 metallothionein-like gene of rice inducible by copper. These results suggest that while OsMT-2 is also involved in cellular response to stress, its function may be complementary to that of OsMT-1.

Towards Understanding Plant Response to Heavy Metal Stress

“…Type 3 MTs are expressed abundantly in the ripe fruits (Clendennen & May, 1997;Ledger & Gardner, 1994;Reid & Ross, 1997), and expression of Type 4 MTs, also known as the Ec type, was only found in developing seeds so far (Chyan et al, 2005;Lane et al, 1987). A vast number of stimuli have been demonstrated capable of inducing MT genes expression in plants, including natural senescence (Bhalerao et al, 2003), hormones like ABA (Reynolds & Crawford, 1996), ethylene (Coupe et al, 1995), wounding and virus infection (Choi et al, 1996), heat shock (Hsieh et al, 1995), sucrose starvation (Hsieh et al, 1996), UV-light (Foley & Singh, 1994), cold and salt stress (Reid & Ross, 1997), etc. Apparently, different types of MTs respond to different factors, which is especially true when treated with heavy metal stress under different concentrations.…”

Examining the Specific Contributions of Individual Arabidopsis Metallothioneins to Copper Distribution and Metal Tolerance

“…In angiosperms, MTs can be classified into four types based on the conserved positions of Cys residues (Cobbett and Goldsbrough, 2002). There are some general trends in the expression of these four types of MTs, with type-1 MTs expressed predominantly in roots, type-2 MTs in leaves, type-3 MTs in fruits, and type-4 MTs in seeds (Zhou and Goldsbrough, 1994;Hsieh et al, 1995;Zhou and Goldsbrough, 1995;Hsieh et al, 1996;Guo et al, 2003). We have previously shown that the genome of Arabidopsis contains seven genes encoding MTs (Cobbett and Goldsbrough, 2002).…”

Molecular Characterization of Metallothionein Genes in Plants.

“…In addition, type 2 MT transcripts preferentially accumulate in aerial tissues, especially leaves, as in soybean MT [27], rice OsMT-2 [9] and LeMTA, LeMTB from tomato [32]. In Vicia faba, Foley and Singh [8] demonstrated through Northern blot analysis that type 2 MT was expressed abundantly in leaves, stems and flowers, and at a low level in roots, but was absent in mesophyll protoplasts.…”

“…For example, the MT in tobacco was strongly induced by tobacco mosaic virus and wounding [7]; and the expression of MT in Vicia faba was reduced when plants were treated with salt, cold, salicylic acid or UV-light [8]. Furthermore, transcripts of OsMT -2 in rice could be induced by sucrose starvation, heat shock and abscisic acid [9]; and the expression of walil in wheat was increased by low-nutrient conditions and wounding [10].…”

“…Class I metallothioneins are the most puzzling and attractive group. Since the first full-length class I MT gene was reported in the flowering plant Mimulus guttatus [25], many more have been identified in a variety of plant species including pea [26], maize [11], soybean [27], Arabidopsis [13,15,28], Vicia faba [8], rape [5], kiwifruit [29], Sambucus nigra L. [4], wheat [10], rice [6,9,12,30], tobacco [7], cotton [31] and tomato [32]. More information on these class I MT genes is shown in Table 2.…”