Abstract:

On the basic of homologous sequences of Camellia japonica，an ascorbate peroxidase
（APX）gene was isolated from the tender leaf in C. azalea by the 3′，5′-RACE technology named
CaAPX1（GenBank Accession ID：KP635267）. The full-length cDNA of CaAPX1 is 1 097 bp，containing
a 753 bp ORF which encodes 250 amino acids. Expression of CaAPX1 in four different heat resistant types
of camellias were analyzed by fluorescent quantitative real-time PCR. The results showed that APX1 gene
was expressed in the four camellias differently，where the expression level of APX1 in C. minutiflora was the highest，medium in C. azalea and C. japonica‘Naidong’，and the lowest in C. reticulata
‘Hentiangao’，which indicated that the expression intensity of the APX1 gene was positively associated
with heat resistance in the different camellia. And fluorescent quantitative real-time PCR analysis also
indicated that CaAPX1 was expressed differently in all examined camellia tissues，and the expression
levels in order were tender leaf，flower，seed embryo and flower bud. The highest expression level of
CaAPX1 was tender leaf，approximately ranging 1.29 to 4.26 times as high as other three groups.
Furthermore，the APX activity in transgenic plants increased 2.58–3.81 fold，and the AsA content
increased 2.67–3.56 fold as higher as wild type. In addition，overexpression of CaAPX1 enhanced heat
stress tolerance in transgenic plants and seeds under high temperature stress.

Key words: Camellia japonica, Camellia azalea, heat resistance, expression analysis, transgenic
tobacco