Proteomic Analysis Of Grafted Cucumber Under Cold Stress For Cold Resistance Mechanism

Cucumber, also known as Courgettes, originates from the subtropics. It is sensitive totemperature variation and is one of the main species used for vegetable production inthe protected lands of the northern cold regions of China. In recent years, with thesoaring demand for the anti-season vegetables, cucumber cultivation area in thegreenhouse is growing in the north of China. But coldness is still the major factoraffecting the yield and quality of cucumber. Researches showed that using rootstockto take grafting cucumber cultivation is an effective way to overcome the chillinginjury. But the cold resistance mechanism of the grafted plants is not clear yet. In thisstudy, grafted cucumber seedlings under cold stress are used as the material.Two-dimensional electrophoresis technology was used to explore the proteinmolecular biological mechanisms of the low temperature resistance of graftedcucumber and to provide a theoretical basis for improving researches of the coldresistance. The main results are summarized as follows:1.In this study we used Yunnan sunspots pumpkin as the rootstock and use Bo jie106cucumber as the scion. Four grafting methods were used to takes experimentalcultivation with cross docking method, cleft grafting method, the traditional graftingmethod and then the improved grafting method–the docking method under the axis.The study compare the combined effect of several grafting methods. The resultsshowed: the docking method under the axis owns many advantages compared withother three grafting methods. For example, the grafting process is simple, and thesurvival rate is high, and the effect is good, the demand for the age of the scion androotstock seedling is low. It is a good artificial grafting method to make it easy to getexperimental grafted seedlings.2.In order to verify that the grafting can improve the cold resistance of cucumber, thisexperiment uses Bo jie106and Bo jie610，two cucumber species, as the scion anduses sunspots pumpkin as the rootstock to get grafted seedlings.Through4℃lowtemperature processing, the study examines some biochemical indexes of graftedseedlings and own-rooted seedlings,including POD activity, MDA accumulation, praline accumulation and so on. The results showed that POD activity in graftedseedlings under cold stress was higher than own-rooted seedlings. And theaccumulation of malondialdehyde (MDA) in two cucumber species was less thanown-rooted seedlings, and the accumulation of praline in two cucumber species wasmore than own-rooted seedlings, and also two kinds of grafted seedlings have muchdifference in low temperature tolerance under low temperature stress. The studyproved that grafted seedlings can indeed improve cold tolerance of cucumber. In thesame time the experiment also illustrates that the advantages of grafted cucumbers arethe combination of the advantages of grafted rootstock and scion.3.In order to understand proteins expressed in grafted cucumbers at low temperatureand explore the biological mechanism of protein molecules about grafted advantage,the experiment uses grafted seedlings and own-rooted seedlings as materials throughthe process of low temperature for48hours. The study analyses differentiallyexpressed proteins in grafted seedlings leaves and own-rooted seedlings leaves anddifferentially expressed proteins in grafted seedlings stems and own-rooted seedlingsstems, and differentially expressed proteins in grafted seedlings roots and own-rootedseedlings roots under low temperature with two-dimensional electrophoresis. Thepreliminary analysis showed: There were60proteins the amount expressed is twicemore than control among which22up-regulated and38down-regulated in the leaves.There were106proteins the amount of differently expressed of which is more thantwice with29overall up-regulated and77overall down-regulated in the stems. Therewere70proteins the amount of differently expressed of which is more than twicewith13overall up-regulated and57overall down-regulated in the roots. It may relateto the mechanism of anti-cold in the grafted seedlings. Meanwhile, the experimentimproved the two-dimensional electrophoresis system for the whole proteins of therelevant organs of cucumber. It will provide some references for cucumbersproteomic researches.