The Component Analysis Of Wax And Suberin And Expression Of Relevant Genes In Exocarp Of ’Dangshansuli’ Pear And Its Russet Fruit Mutant

‘Dangshansuli’pear fruit has a green yellow skin while its mutant‘Xiusu’pear has a russet fruit skin,which is a genetic variation.In order to further study the formation mechanism of‘Dangshansuli’russet skin,this paper takes the exocarps of‘Dangshansuli’pear and its russet mutant‘Xiusu’in different days after full bloom as the test materials,studies on fruit development,fruit dot development,fruit chromatism and hardness were performed.The fruit epidermal structure were also determined by microscope.The composition of wax and suberin of fruit peel were mensurated by the gas chromatography mass spectrum（GC-MS）too.The relative expressions of the key genes in wax and suberin biosynthesis were analyzed by using real-time quantitative reverse transcription-PCR.The main results were as followed:（1）At the 175 days after full bloom（DAFB）,the surface area and the fresh weight of‘Xiusu’pear fruit were significantly bigger than‘Dangshansuli’pear fruit.With the development of fruit,the chromatism between‘Dangshansuli’fruit and‘Xiusu’fruit increased,the fruit hardness of‘Xiusu’were close to‘Dangshansuli’.‘Dangshansuli’fruit cuticle evenly distributed on the fruit peel,and its maximum thickness were at the 175d.There were less‘Dangshansuli’fruit epidermal cells suberized,while the suberized epidermal cells of‘Xiusu’fruit were increased with the development of fruit.‘Xiusu’fruit cuticle unevenly distributed on the fruit peel,and easily cracked and shed.‘Dangshansuli’and‘Xiusu’showed different fruit dot development pattern,in which the fruit dot on‘Xiusu’fruit formed earlier and more intensively,developed faster and had the larger size than‘Dangshansuli’fruit dot at the same developmental stage,whereas fruit dot on Green‘Dangshansuli’fruit formed later,developed slower.（2）The analysis of the cuticular wax of‘Dangshansuli’and‘Xiusu’indicated that alkane was the main component and kept odd predominance.The C₂₉ was the main alkane.Since 50 DAFB,the relative content of alkane of‘Dangshansuli’wax was higher than‘Xiusu’and the gap increased with the development of fruit,while the relative content of fatty acids of‘Xiusu’wax was higher than‘Dangshansuli’and the gap increased with the development of fruit too.In the whole fruit development period,the relative content of fatty alcohol of‘Dangshansuli’wax was lower than‘Xiusu’.The relative content of terpenoid of‘Dangshansuli’wax was close to‘Xiusu’except for 125 DAFB.（3）The analysis of the suberin of‘Dangshansuli’and‘Xiusu’fruit peel indicated that suberin of pear was composed of fatty acid,α,ω-diacids,ω-hydroxy fatty acids,mainly ferulic acid and primary alcohols.During the early stage of fruit development,fatty acids were the main components of fruit suberin.At the late stage of fruit development,α,ω-diacids were the main components of‘Xiusu’,while the main components of‘Dangshansuli’still were fatty acids.At 175 DAFB,the content ofα,ω-diacids,ω-hydroxy fatty acids and ferulic acid of‘Xiusu’higher than other days,and was about three times higher than‘Dangshansuli’.The ferulic acid appeared at100 DAFB in‘Xiusu’suberin,while appeared at 150 DAFB in‘Dangshansuli’suberin.At 175 DAFB,the relative content of primary alcohols of‘Dangshansuli’was30.6%,while only 3.7%in‘Xiusu’suberin.（4）Semi-quantitative RT-PCR indicated that expression of KCS1 in the exocarp of‘Dangshansuli’was higher than that in‘Xiusu’except for 50 DAFB.The expression of PbECR、PbFAR and PbWSD1 in the‘Dangshansuli’was higher than that in‘Xiusu’at 25,50,or 75 DAFB.The expression of PbCYP86A1 and Pb4CL in‘Xiusu’was higher than that in‘Dangshansuli’at 25,50,or 75 DAFB,and is significant positive correlation with the suberin content of‘Xiusu’.