Page 8 - Molecular Plant Breeding

Molecular Plant Breeding 2011, Vol.2, No.16, 109-118
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Figure 2 Alignment analysis of nucleotide sequences among 11
cloned SCA from lily
Note: “*” showed the same nucleotide; black underlines showed
primer sequences and red underline showed the nucleotide
sequences which encode signal peptide. Introns were framed in
black box. Yellow boxes showed starting codon “ATG” and
terminate codon “TAA” respectively. The figures in the end
showed the base pair numbers of the nucleotide sequences
were the alanine (A) in the 71st site, Oriental lily was
the glycine (G), Whereas SCA from Lilium longiflorum
'Nellie white' and LlSCA1 and LlSCA2 from the
'White heaven' in the 71 st site were the alanine (A),
LlSCA3 from 'White heaven' was the alanine (A),
which was in line with SCA3 of three subtype of SCA
isolated from Lilium longiflorum 'Nellie white' by
Chae et al (2007) also was the alanine (A) the site of
82nd amino acids was the serine (S) in lily except for
'Nellie white' was the arginine (R) identified in
GenBank. It remains to be verified whether the
differences in the amino acids among the species
occurs in the functional regions of protein resulting in
the differences in pollen adhesion and influences on
the directional pollen tube growth, then leading to
generate the phenomenon of incompatibility.
In the sequence structure of the proteins, the cloned
fragments contains the common structural features of
LTP, including eight conserved cysteine residues and
two conserved pentapeptide motifs (Thr/Ser-X1 -X2-
Asp-Arg/Lys and Pro-Tyr-X-Ile-Ser) (Douliez et al.,
2000). However, the first amino acid of LaSCA4 and
LlSCA3 was asparagine in the first motif instead of
threonine or serine, which was consistent with the site
of rice LTP. The second motif, the first amino acid of
LlSCA1 was leucine instead of proline, there was only
one difference in the site of amino acid between
LlSCA1 and LlSCA2. According to nucleotide sequence
analysis, we found that the 325th base in LlSCA1 was
T while in LlSCA2 and LlSCA3 were the C. Nucleotide
sequence analysis of LaSCA2 found that the 112 nd
nucleotide mutated from C to T leading to the fifth
amino acid coding sequence transformed from CAG
(glutamine) to TAG (stop codon), resulting in early
translation termination. In order to further analyze the
subsequent sites and to judge whether the conserved
structural features of LTP occurred, the whole
sequence still used to be the sequence alignment in
Figure 3, the results found that the sequences behind
the mutating bases had no any changed in encoding
amino acids, so we preliminary judged that the
mutagenesis on the site might have occurred, resulting
in translation termination, and further speculated that
LaSCA2 might be a pseudo-gene occurred during the
evolution process of SCA. For maize LTP, the 46th of