LEA5 gene was postulated related with both stress and hormone responses. In an attempt to find genes exclusively expressed during fruit ripening of Cara Cara navel orange, a novel cDNA clone encoding late embryogenesis-abundant protein 5 like gene （CitLEA5-1） was obtained. It was 582 bp in length, containing 97 deduced amino acids. Compared with the stress-induced LEA5 from leaves of Citrus sinensis, CitLEA5-1 had a shorter 3′ untranslated region （UTR）. Semi-quantitative RT-PCR analysis revealed that CitLEA5-1 was transcriptional regulated during fruit ripening of Cara Cara navel orange.
Abundance of simple sequence repeat (SSR) in Citrus sequences from EMBL database was investigated by usingcomputer program MISA (MIcroSAtellite), which aimed to provide useful information for the development of SSR markers.Among 32 896 sequences of Citrus, 4 987 SSRs were found in 4 167 sequences and the average distance between SSRs wasapproximately 3.5 kb. Mononucleotide repeats (50.6%) were the most abundant repeats. And di-, tri-, tetra-, penta- andhexa-nucleotide repeats were 22.8, 25.2, 1, 0.08, and 0.36%, respectively. The most abundant motif was A/T followed indescending order by AG/CT, AC/GT, AT/TA. AAT/ATT, AAG/CTT, AGC/CGT, ACG/CTG and C/G. They comprised about90% of all microsatellites. Ten primer pairs were designed, and three of them produced clear visible bands among Citrusand its related genera.
A cDNA library was constructed end characterized from the pulp of Cera Care navel orange （Citrus sinensis Osbeck） at different stages of ripening. Tittering results revealed that approximately 5.086×10^5 independent clones were included in this library. Electrophoresls gel results of 15 randomly selected clones revealed that the size of the insertion fragments ranged from 400 bp to 2 kb, with an average size of 900 bp. Sequencing results of 150 randomly picked clones showed that the recombination rate was 94%. During subsequent sequence analysis, 41 of 139 clones failed to be identified end the amino sequence of 71 clones shared less than 30% identity with related plants in GenBank. Of 27 clones whose amino sequences shared more than 60% identity with other related plants in GenBenk, 17 clones showed an 80% identity with the corresponding candidate genes of citrus. The clone recognized as the type Ⅲ metallothlonein-llke （MT） gene was observed to occur 13 tlmes, Indlcatlng that the protein may play an important role In frult development and rlpenlng.
