TheArabidopsis thaliana Myo-Inositol 1-Phosphate Synthase1 Gene Is Required forMyo-inositol Synthesis and Suppression of Cell Death

Abstract

L-myo-inositol 1-phosphate synthase (MIPS; EC 5.5.1.4) catalyzes the rate-limiting step in the synthesis of myo-inositol, a critical compound in the cell. Plants contain multiple MIPS genes, which encode highly similar enzymes. We characterized the expression patterns of the three MIPS genes in Arabidopsis thaliana and found that MIPS1 is expressed in most cell types and developmental stages, while MIPS2 and MIPS3 are mainly restricted to vascular or related tissues. MIPS1, but not MIPS2 or MIPS3, is required for seed development, for physiological responses to salt and abscisic acid, and to suppress cell death. Specifically, a loss in MIPS1 resulted in smaller plants with curly leaves and spontaneous production of lesions. The mips1 mutants have lower myo-inositol, ascorbic acid, and phosphatidylinositol levels, while basal levels of inositol (1,4,5)P 3 are not altered in mips1 mutants. Furthermore, mips1 mutants exhibited elevated levels of ceramides, sphingolipid precursors associated with cell death, and were complemented by a MIPS1-green fluorescent protein (GFP) fusion construct. MIPS1-, MIPS2-, and MIPS3-GFP each localized to the cytoplasm. Thus, MIPS1 has a significant impact on myo-inositol levels that is critical for maintaining levels of ascorbic acid, phosphatidylinositol, and ceramides that regulate growth, development, and cell death.

Genome-Wide Association Mapping of Fertility Reduction upon Heat Stress Reveals Developmental Stage-Specific QTLs in Arabidopsis thaliana

“…Four of those SNPs were included in the GWA mapping and were moderately associated (2log(P value)>4) with heat stress response in region C. The strongest associated SNP is responsible for a nonsynonymous change in the protein sequence of AT5G10170, which codes for MyoInositol 1-Phosphate Synthase3 (MIPS3). MIPS3 expression was most prominent in vascular tissue (Donahue et al, 2010), and heat-induced expression was reported during the seedling stage (Khurana et al, 2012). The Arabidopsis genome has three MIPS genes.…”

“…FRI-sf2 (CS6209) can also be obtained from the ABRC Stock Center. In addition, the following SALK T-DNA insertion mutants (Alonso et al, 2003) and GABI-Kat T-DNA insertion mutants (Kleinboelting et al, 2012) were obtained from NASC: qul2-2 (SALK_065604c), AT2G03505 (GABI_745A07), AT2G03490 (SALK_125910), mips3-2 (SALK_120131c; Donahue et al, 2010), and AT5G10200 (SALK_040912c). Seeds of the mutants qul1-1 and qul1-1 qul2-1 were kindly provided by L. Østergaard (Fuentes et al, 2010).…”

Comparative Expression and Cellular Localization of Myo-inositol Phosphate Synthase (MIPS) in the Wild Type and in an EMS Mutant During Common Bean (Phaseolus vulgaris L.) Seed Development

“…Moreover, compared with wild type, all EMS mutant seeds are wrinkled and empty. Interestingly, similar phenotypes have been showed in Arabidopsis mips mutants (Donahue et al 2010) which show a significant percentage of wrinkled and empty seeds compared with their corresponding wild-type accessions. During wild-type embryogenesis (Fig.…”

“…, Pisum sativum (Imhoff and Bourdu 1973), Vigna radiata (Adhikari et al 1987;Wongkaew et al 2010), Oryza sativa (Hait et al 2002), Glycine max (Iqbal et al 2002), Citrus paradisi (Abu-abied and Holland 1994), Sesamum indicum (Chun et al 2003), Arabidopsis thaliana (Johnson 1994), Passiflora edulis (Abreau and Aragao 2007), and Phaseolus vulgaris (Wang and Johnson 1995). Although yeast and animal genomes contain a single gene encoding MIPS (GhoshDastidar et al 2006;Donahue et al 2010), plant have multiple MIPS genes (Torabinejads and Gillaspy 2006;Donahue et al 2010). In common bean, three sequences encoding MIPS gene have been reported: PvMIPSs (GenBank accession AJ853494), expressed mainly in developing seeds; PvMIPSr (GenBank accession U38920), expressed mainly in roots (Wang and Johnson 1995;Johnson and Wang 1996); and PvMIPSv (GenBank accession FN356964), expressed in vegetative organs, especially leaf tissues (Fileppi et al 2010).…”

“…Myoinositol is the most important and abundant stereoisomer of the six-carbon cyclitol inosito (Luo et al 2011) and acts as a substrate for the formation of various inositol-derived molecules involved in many different and critical plant biochemical and physiological pathways, such as intracellular signal transduction (Stevenson-Paulik et al 2005), membrane construction and trafficking (Cullen et al 2001), and regulation of cell death (Donahue et al 2010). More recently, myo-inositol was reported to be the main substrate for synthesizing membrane phosphatidylinositol and phosphatidylinositides, which are essential for endomembrane structure and trafficking and thus for auxin-regulated embryogenesis (Luo et al 2011).…”