Studies On Molecular Markers Of Sex Expression In Cucumber (Cucumis Sativus L.)

Cucumber (cucumis sativus L.) is a classic materias used in studying sexexpression, which is not only controlled by genetic factors, but also regulated byenvironments and chemicals. Long-day, high-temperature and gibberellins canaccelerate the formation of staminate flowers, while short-day, low-temperature andethylene can accelerate that of gynoecious flowers. Endogenous ethylene, which hasbeen proved to be significantly positive-correlated with the formation of gynoeciousflowers, is named as "sex hormone" of cucumber. It was indicated that ethyleneinsensitive 3 (EIN3) was a downstream factor related with signal transduction ofethylene, which was localized in cell nucleus. Its coded EIN3 protein can activate thetranscription of some genes related with ethylene reaction, which was realized bycombinating with the special sequence in their promoters. Based on these above, apair of nero-isogene materials of cucumber, WI1983G (female) and WI1983H(hermaphrodite), and their F₂ progeny population were used in selecting andanalyzing SNP marker of EIN3, clarifying the theory of sex expression of cucumberby RFLP-Bfm I, selecting polymorphic bands in the whole genome DNA. The mainresults were as follows:(1) Two SNP markers were obtained after analyzing the sequence of EIN3 ofWI1983G and WI1983H. Special PCR amplifications have been carried out with two groups of new-designed primers, Groupâ… (Forward primer: 5'-cat gat ggg atc ttgaag-3', Reverse primer: 5'-cac cat tcc tcg act cca-3')and Groupâ…¡(Forward primer:5'-cat gat ggg atc ttg aag-3', Reverse primer: 5'-ata ata gca agc cag gta gc-3'). Theresults have showed that the special amplified product only appear in the female ones.That is, A 382 bp band could be found with Groupâ… and a 605 bp band could befound with Groupâ…¡. Besides, the sex star in the field indicated that the ratio betweenfemales and hermaphrodite is about 3:1, which accord with the rule of segregation(x²ï¼œ0.05). According to the model of Yin and Quinn, it can be primarily speculatedthat the genotype of females is FFMM and that of hermaphrodite is FFmm. Both ofthe two markers can be used for selecting the female varieties of cucumber.(2) EIN3 gene sequences of WI1983G and WI 1983H were far more analyzed byRFLP-Bfm I. The results showed that the digested products were all 500 bp of bandfor hermaphrodite varieties (named as "aa"). For female varieties, two types of bandsoccurred. That was, two main products of 497 bp and 608 bp(named as "Aa") and aproduct of 608 bp (named as "AA"). The sex stat in the field indicated that the ratioamong AA, Aa and aa is about 1:2:1(x²ï¼œ0.05). This proved more that the genotype ofWI1983G is FFMM and that of WI1983H is FFmm. The sex of F₂ progeny populationsegregated with the segregation of M/m.(3) No different RAPD bands have been found among 600 primers.Using AFLP,five polymorphic bands between WI 1983G and WI 1983H were obtained, which wererespective CT_TG_480bp, CA_AT_500bp, CA_AT_520bp, CA_AT_680bp and CA_AT_700bp.The results could be used for seeking the genes related with sex expression ofcucumber.