COI1 affects myrosinase activity and controls the expression of two flower-specific myrosinase-binding protein homologues in Arabidopsis

Abstract

Two cDNA clones homologous to myrosinase-binding proteins (MBPs) were identified by differential display in Arabidopsis thaliana (L.) Heynh. The cDNAs (MBP1 and MBP2) correspond to two open-reading frames found in a gene cluster of seven putative MBP genes located on chromosome 1. The predicted proteins MBP1 and MBP2 are similar to lectins and plant aggregating factors. In addition. MBP2 contains a region of high content of proline and alanine residues, commonly found in arabinogalactan proteins and hydroxyproline-rich glycoproteins. Transcripts corresponding to MBP1 and MBP2 genes are exclusively and abundantly expressed in flowers but are not detected in male-sterile flowers of coi1 plants, insensitive to jasmonic acid. Northern analysis and in situ hybridization revealed that MBP mRNAs are present in higher levels in immature flowers and are localized in several floral organs, including the ovary, ovules, style, anthers and filament. Transcripts of the Arabidopsis myrosinase gene TGG1 show a pattern of expression similar to that observed for the MBP genes during flower development; however, they are also abundant in green tissues and are only partially affected by COI1. Crude preparations of soluble proteins from leaf and flower extracts of wild-type Arabidopsis showed myrosinase activity when sinigrin was used as substrate. In contrast, coi1 plants showed significantly reduced myrosinase activities in both leaves and flowers. The results show that COI1 controls MBP expression in flowers and significantly affects the expression and activity of myrosinase in Arabidopsis.

The Identification of Candidate Genes for a Reverse Genetic Analysis of Development and Function in the Arabidopsis Gynoecium

“…2R). Tapetal expression of Pup10 (MBP2) is also apparent in the in situ analysis performed by Capella et al (2001), although the precise location of the expression of this gene in the inner epidermis and ovule integuments, clearly demonstrated in the present work, is not clear from the in situ hybridization data presented by Capella et al (2001).…”

“…The Pup10 cDNA has been previously characterized (Capella et al, 2001) and termed MPB2 on the grounds of similarity between its predicted protein and a characterized MBP from canola (Brassica napus; Taipalensuu et al, 1997). The Pup2/MBP2-predicted protein shows 47.2% amino acid similarity to this MBP from canola and is the most similar predicted protein to the canola MBP that exists in the Arabidopsis predicted proteome.…”

Expression profiling reveals COI1 to be a key regulator of genes involved in wound- and methyl jasmonate-induced secondary metabolism, defence, and hormone interactions

“…The MeJAinducible genes encoding vegetative storage protein (At5g24770 - Benedetti et al, 1995), thionin 2.1 (At1g72260 - Bohlmann et al, 1998), coronatineinduced protein (At1g19670 - Benedetti et al, 1998), myrosinase binding protein At1g52030 (Capella et al, 2001), and the jasmonate synthesis genes LOX2 (At3g45140 - Bell and Mullet, 1993), allene oxide synthase (At5g42650 - Laudert and Weiler, 1998), and OPDA reductase (At2g06050 - Sanders et al, 2000;Stintzi and Browse, 2000) were induced by both MeJA and wounding (Table SI). Genes such as PR5 (At1g75040) and PDF1.2 (At5g44420), which require both MeJA and ethylene for high levels of expression (Xu et al, 1994;Penninckx et al, 1998), were not significantly upregulated by MeJA alone.…”

Genotype, Age, Tissue, and Environment Regulate the Structural Outcome of Glucosinolate Activation

“…Such modularity could be mediated by members of a gene family each acting in a limited set of tissues, a result of an evolutionary process called subfunctionalization (Hughes, 1994;Lynch and Force, 2000;Fraser et al, 2002). There are numerous Arabidopsis genes homologous with ESP, ESM1, and the myrosinase binding proteins, all with different tissue-specific expression patterns (Capella et al, 2001;Zhang et al, 2002;Barth and Jander, 2006). However, the homologs of ESP and ESM1 have no demonstrated function, so further experiments are required to test their importance in the tissue-specific regulation of structural outcomes.…”