Observation Of Pericarp And Analysis Of Differential Expression Genes Of ’Dangshansuli’ And Its Mutant ’Xiusu’

‘Dangshansuli’ pear （Pyrus bretschneideri cv. Dangshansuli）was a main cultivar with over a cultivation history of250years. A mutant of ‘Dangshsuli’ discovered in2005and called as ‘Xiusu’ had russet fruit skin and unique flavor, and was also an outstanding stable mutant of ‘Dangshansuli’ pear. There was only quite a few papers published on the research of fruit skin color in pear, and many of them was focused on the physiological aspect in the green and red skin pears. The pericarp structures of ‘Dangshansuli’and ‘Xiusu’ pear was observed under microscope, scan electronic microscope （SEM） and transmission electronic microscope （TEM）. The total RNA was extracted from pericarp of ‘Dangshansuli’and ‘Xiusu’ pear at5stages, and the gene differential expression was studied by the techniques of mRNA Differential Display PCR. The achievement of this experiment will lay a foundation for mechanism study of russet skin formation and improvement of pear fruit color.The main results were gained as follows:1. The pericarp of ‘Dangshansuli’ pear has a smooth and yellow-green surface, while that of ‘Xiusu’ pear has a coarser and russet surface. Under SEM telescope, it was observed that the arrangement of pericarp cell in ‘Dangshansuli’ was looser with larger cracks on cuticle in size of100³00μm, while that in ‘Xiusu’ was tighter with smaller cracks on cuticle in size of10¹00μm. The cell inter space of pericarp in ‘Dangshansuli’ was bigger, and the cell wall was thiner than that in ‘Xiusu’ pear, some of the pericarp cells were full of hypmetabolic substances.2. The DDRT-PCR system for Differential Display of mRNA from pericarp of ‘Dangshansuli’and ‘Xiusu’ pear was optimized by orthogonal design as the following conditions: pre-denaturation at94oC for2min, denaturation at94℃for30s, with anneal at40℃for2min,40s extension at72℃for40seconds followed by35cycles,7min extension at72℃, reservation at4℃. the total volume of PCR system was25μl incloding dNTP concentration of0.1mmol L^-1, random and fixed primers at concentration of0.5μmol L^-1, Mg⁺²concentration3mmol L^-1 and0.5U Taq polymerase.3. There were63differential fragments cloned from pericarp of ‘Dangshansuli’and ‘Xiusu’ pear,60of them were in good quality and the other3fragments were inferior. According to Gene Ontology, the sequences of the60ESTs were composed and analyzed by Blast software online, and11Contigs （ESTs numbers≥2） sequences and22Singlets （ESTs numbers=1） were screened out with the novelty of55%.4. It was testified by real time PCR, with the template of cDNA reversely transcribed from mRNA extracted from pericarp of ‘Dangshansuli’and ‘Xiusu’ pear at75,100,125,150and175days after full bloom, that the relative expression quantity of α-tubulin gene and calmodulin gene were higher in pericarp of ‘Xiusu’ than in ‘Dangshansuli’.