The Arabidopsis Spontaneous Cell Death1 gene, encoding a ζ-carotene desaturase essential for carotenoid biosynthesis, is involved in chloroplast development, photoprotection and retrograde signalling

Abstract

Carotenoids, a class of natural pigments found in all photosynthetic organisms, are involved in a variety of physiological processes, including coloration, photoprotection, biosynthesis of abscisic acid (ABA) and chloroplast biogenesis. Although carotenoid biosynthesis has been well studied biochemically, the genetic basis of the pathway is not well understood. Here, we report the characterization of two allelic Arabidopsis mutants, spontaneous cell death1-1 (spc1-1) and spc1-2. The weak allele spc1-1 mutant showed characteristics of bleached leaves, accumulation of superoxide and mosaic cell death. The strong mutant allele spc1-2 caused a complete arrest of plant growth and development shortly after germination, leading to a seedling-lethal phenotype. Genetic and molecular analyses indicated that SPC1 encodes a putative z-carotene desaturase (ZDS) in the carotenoid biosynthesis pathway. Analysis of carotenoids revealed that several major carotenoid compounds downstream of SPC1/ZDS were substantially reduced in spc1-1, suggesting that SPC1 is a functional ZDS. Consistent with the downregulated expression of CAO and PORB, the chlorophyll content was decreased in spc1-1 plants. In addition, expression of Lhcb1.1, Lhcb1.4 and RbcS was absent in spc1-2, suggesting the possible involvement of carotenoids in the plastid-to-nucleus retrograde signaling. The spc1-1 mutant also displays an ABA-deficient phenotype that can be partially rescued by the externally supplied phytohormone. These results suggest that SPC1/ZDS is essential for biosynthesis of carotenoids and plays a crucial role in plant growth and development.

Involvement of sphingoid bases in mediating reactive oxygen intermediate production and programmed cell death in Arabidopsis

“…Analysis of gene expression by real time-PCR was performed essentially as previously described [40]. Primers used in the experiments described in Figure 3A and 3B were (all sequences are from 5′-to 3′-end): P1: GCA GAG TCA GTA GCT TGA AGA TGT P2: CGG CAA CAA CAC TAA GCT ACT TGA P3: ACC AGA GAC TTA GCA GTT CAG GA P4: CAA TAG GTG ATT CCC GGT TGC TTG…”

Disruption of the 1-deoxy-D-xylulose-5-phosphate reductoisomerase (DXR) gene results in albino, dwarf and defects in trichome initiation and stomata closure in Arabidopsis

“…Exogenous application of GAs to the medium could partially rescue the dwarf phenotype of the pds3 mutant [30]. Other research indicated that levels of not only GAs but also other important compounds were decreased as a result of the metabolic disruption in the mutants of enzymes involved in the MEP pathway [21,[30][31][32][33][34]. However, no detailed analyses have been [30]).…”

ArabidopsisHistidine Kinase CKI1 Acts Upstream of HISTIDINE PHOSPHOTRANSFER PROTEINS to Regulate Female Gametophyte Development and Vegetative Growth

“…Analysis of gene expression by qRT-PCR was performed as previously described (Dong et al, 2007;Feng et al, 2007). Briefly, the first-strand cDNA was synthesized using ;1 to 2 mg of total RNA primed by oligo(dT).…”

“…After the staining, the sample was analyzed under a confocal microscope. Dark-induced leaf senescence was analyzed as described previously (Dong et al, 2007;Feng et al, 2007).…”