Study Of The Low Rate Of Fruit Set In Juglans Hopeiensis And The Influence Of Abscisic Acid On Tomato Fruit Set

Fruit is an indispensable part of the people’s diet.In recent years,with the improvement of living standards,the demand of the fruit are also gradually increased.And people are constantly pursuing high quality,nutritious fruit.Therefore,planting fruit yield and quality is very important.The development of male and female flowers as well as pollination and fertilization directly restrict the fruit yield and quality,such as the Juglans hopeiensis Hu(J.hopeiensis).The nut of Juglans hopeiensis Hu(J.hopeiensis)is favored by consumers for its hard shell,beautiful texture and high ornamental value.However,it has poor fruit set,which restricts expansion of the industry of it in China.We compared the development of pistillate and staminate flowers of J.hopeiensis(Juglthiss hopeiensis,’M1’ and ’M59’)with those of J.regia(English walnut,’Liaoning l’and ’Lvbo’)and J mandshurica(Manchurian walnut,’Qiuzi 1-17’).These last two species generally have a high rate of fruit set.Pollen in the J hopeiensis was dysplastic,irregular in shape and sometimes empty,whereas pollen in the two other species were subglobose when mature and generally full.The embryo sac eventually disappeared in the two J.hopeiensis,whereas they were well developed in the other two species.The results suggested that abnormal development of pollen and embryo sac contribute to poor fruit set in J hopeiensis.Here,to explore the plant hormone abscisic acid in the role of tomato male and female flower organ development,we based on the Solanum lycopersicum cv Jia Bao tomato as the experiment material,and using the RNA interference technology to inhibit the expression of SlNCED1 gene coding key enzyme of ABA synthesis in tomato plant.Through the observation and comparative analysis,we explored the reasons of low fruit setting rate in Juglans hopeiensis Hu and provide the theory basis for solving problems of its low fruit setting rate and low yield.We use the real-time quantitative PCR technology tested the two coding ABA key enzyme genes(SlNCED1 and SlNCED2)and three ABA degradation of metabolic enzyme gene(SlCYP707A1,SlCYP707A2 and SlCYP707A3)in tomato flower organs.In the process of tomato anther development and mature,the absolute expression quantity of SlNCED1 and SlCYP707A1 is the highest,which is the main effect gene of the SINCEDs and the SlCYP707As gene family,respectively.And the expression of SlNCED1 and SlCYP707A1 is gradually increased as the development of the anther,which showed that ABA related metabolism is very active in anther’s development and maturation and may affect the tomato anther development and maturity,To test the role of ABA in the anther development,we inhibited the synthesis of endogenous ABA in tomato using the plasmid carrier of SlNCED1-RNAi which is driven by the promoter of SlE8.By using agrobacterium infect tomato callus,we gain four independent transgenic plants strain which were used as the experimental material for physiological,biochemical and molecular detection.Results show that the endogenous ABA content of the transgenic tomato flower organ was reduced for 30-50%.Compared with the control group,the transgenic tomato flower bud,sepal and petals were larger,significantly,and the style was shorter and bolder.More obviously,the transgenic tomato anther development malformed and atrophic,and could not form the normal pollen sac.The ovary of the transgenic tomato appears malformed.Observation of microscopic section analysis shows that,there was no significant difference between the transgenic tomato flower organ and the control group during the development of sporogenous cell,microsporocyte,tetrad and microspore stage.But during the period of microspore to the pollen grain,most of the f microspore in the transgenic tomato flower organ failure to transform the normal pollen grain,but become the irregular shape,inconsistent size,abnormal pollen grains.With the development of the flower organ more and more microspore became abnormal pollen grains.To mature stage,normal pollen in the clinandrium is only about 10%less.The gene expression analysis showed that,the pollen development necessary gene in transgenic tomato anther expressed lower than the control group.In the pistils,the absolute expression quantity of SINCED1 and SICYP707A1 is the highest,which is the main effect gene of the SINCEDs and the SlCYP707As gene family,respectively.We found that the inhibition of SlNCED1 makes the fruit-set rate of tomato greatly reduced(less than 10%).And transgenic tomato fruit have no seed belong to parthenocarpy.And the flowering period was extended,the ovary began to extend before the flowering.In addition,by the inhibition of SINCED1 the endogenous ABA content in the transgenic tomato flower organs was reduced.Therefore,the transgenic tomato ovary was easily influenced by low temperature to produce deformity of the ovary,and cause dehiscent fruit,etc.We use the in situ hybridization technique to test the space-time location of SINCED1,we found that the SINCED1 mainly expressed in new meristem during the flower bud differentiation phase such as petal primordium,stamen primordia and pistil primordium.In the development of flower bud,the SINCED1 mainly expressed in the ovule,stigma,anther,and sepal.These results showed that the formation and development of flower organs require the participation of hormone ABA.To sum up,ABA plays an important role in the development of in tomato female/male flower organs.In conclusion,through the observation and comparative analysis on the female/male reproductive organs,we explored the reasons of low fruit setting rate in Juglans hopeiensis Hu and provide the theory basis for solving problems of its low fruit setting rate and low yield.And this study first carry out the research of the influence of abscisic acid on the development female/male reproductive organ,and try to shed light it on the molecular level.The conclusion obtained here filled the blank of role mechanism of abscisic acid in plant reproductive organ development for a long time,provided a molecular basis for the understanding the role of abscisic acid in plant growth and development,and more enriched the role of abscisic acid in plant growth and development process.