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demand of geranyl-geranyl-pyrophosphat (GGPP) by the carotenoid
biosynthesis pathway since GGPP is the common precursor for both GA
and carotenoid biosynthesis (Rodriguez-Concepcion et al. 2001). However,
the contribution of carotenoid synthesis to the regulation of balance between
ABA and GA is still elusive (Fang et al. 2008).
The
non-dormant-1
(
nd-1
) mutant in sunflower, characterized by an albino
and viviparous phenotype, was isolated by selfing an in vitro-regenerated
plant (Pugliesi et al. 1991). Pigment analysis by HPLC demonstrated the
absence of ß-carotene, lutein and violaxanthin (Conti et al. 2004). In addition,
nd-1
seedlings grown under very dim light conditions showed a strong
accumulation of ζ-carotene and to a lesser extent, of phytofluene and cis-
phytoene. All this suggested that ζ-carotene desaturation was impaired.
Therefore, Conti et al. (2004) cloned and characterized the ξ-carotene
desaturase (
Zds
) gene by a candidate gene approach. Amino acid sequences
of cloned
Zds
genes from
Tagetes erecta
(GenBank AF251013),
Arabidopsis
thaliana
(AF121947),
Narcissus pseudonarcissus
(AJ224683),
Solanum
lycopersicum
(AF195507),
Capsicum annuum
(X89897) and
Zea mays
(AF047490) were aligned. Regions with the highest conservation were
identified and two primers were designed. Total RNA was used for first
strand cDNA synthesis using a Superscript preamplification kit. The RACE
approach was used to isolate the 5' and 3' ends of the
Zds
cDNA. The
putative full-length
Zds
cDNA was obtained by PCR using specific primers
at the extreme 5' end. To isolate the full-length exons/introns region of the
Zds
gene, sequence information from cDNA was used to design specific
primers for PCR amplification from genomic DNA. The
H. annuus Zds
gene
(GenBank accession no AJ514406) consists of 14 exons and 13 introns, 44
nucleotides of 5'-untranslated region (UTR), and 26 nucleotides of the 3'-
UTR, covering a total of 5,020 bp. RT-PCR analyses showed that
nd-1
plants
did not accumulate
Zds
transcripts. Based on genomic Southern
hybridizations, the
nd-1
genome might contain a large deletion at the
Zds
locus (Conti et al. 2004).
6.3.2.3 Pistil- and Pollen-specific Genes
LIM proteins contain one or several LIM domains - double zinc-finger
motifs with the sequence C-X
2
-C-X
17-19
-H-X
2
-C-X
2
-C-X
16-24
-C-X
2
-(C, H, D) -
which are often found in the same protein together with another functional
domain, such as a homeodomain or a kinase domain (Taira et al. 1995). The
acronym LIM is derived from the three homeodomain proteins first
recognized as sharing this structural feature (Gill 1995):
lin-11
, which
functions in asymmetric division of
Caenorhabditis elegans
(Freyd et al. 1990);
isl-1
, which has a major function in motor neuron development in rat
(Karlsson et al. 1990); and
mec-3
, which is essential for proper differentiation
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