Study On The Mechanism Of Temperature Effect On Fruit Shaping In Fingered Citron

Fingered citron(Citrus medica L.var.sarcodactylis Swingle),belongs to citrus spp.of Rutaceae family,a variant of citron(C.medica L.),has a close genetic relation with citron,while they show huge difference in fruit shape.It was found in priliminary experiments that a high temperature(20℃)induced the fist(shape)fruit,but a low temperature(4℃)induced the finger(shape)fruit during the flowering stage,and the CRC gene of fingered citron is involved in the fruit shaping of the temperature response.The purpose of this project is to unravel the internal mechanism of temperature effect on fruit shaping in fingered citron.The results are discribed as follows:1.Based on the fruit shape data in fingered citron passed the winter under differnt regons,we established the standard of fruit shape phenotyping in fingered citron: Fruit Longitudinal diameter(L),the Length of the Regions with No Obvious Division at the Base of Fruit(NOD),Proportion of the Regions with No Obvious Division at the Base of Fruit to the Longitudinal Diameter(PNOD),The Sum of Left and Right Maximum Expansion Angles of Fruit(SMEA),The Number of Separated Fingers(NSF),Finger Seam Depth(FSD),The Number of Deep Finger Seam(NDFS),The Number of Light Finger Seam(NLFS),The Proportion of Light Finger Seam(PLF),was established.In addition,through the coordinate axis classification tool of ‘fist(shape)→ finger(shape)’,it can be used to classify the fruit shape in fingered citron in the future.2.According to the standard,the fruit shape in fingered citron after overwintering in Jinhua and Lingshui are counted,and then the relationship between the fruit shape and the accumulated chilling hours was mined.The fruit shape of 0 / 1 / 2 / 3 / 4 month group(LT 0 / 1 / 2 /3 / 4 for short)of Jin Hua low temperature treatment are classified,with the accumulated chilling time are ranked as LT 0 / 1 / 2 /3 / 4 from low to high.The PNOD of the LT 0 / 1 / 2 /3 /4group decreased gradually,indicating that accumulated chilling hours were negatively correlated with the proportion of areas where fruit division was not obvious.The SMEA of the LT 0 / 1 / 2 /3 / 4 increases gradually.That is to say,the degree of fruit expansion is positively correlated with the accumulated chilling hours.The NSF of the LT 0 / 1 / 2 /3increases gradually.Thus,the number of fingers is positively correlated with the accumulated chilling hours.Calculating the PLF values of each group,it was found that the degree of finger splitting or surface depression was deepened with the increase of accumulated low temperature time.The above data show that the accumulated chilling hours will make the fruit shape be a fist shape,otherwise it will be a finger shape.3.According to the relationship between different accumulated chilling hours and the fruit shaping in fingered citron,it can be divided into four types: A(approximate finger shape),B(transition finger shape),C(transition fist shape)and D(approximate fist shape).The rapid growth phase of fingered cirton(longitudinal growth period)determines the value of PNOD,and the transverse growth period determines the size of SMEA.Due to the different time points and durations of longitudinal and transverse growth periods growth focused periods,PNOD and SMEA will produce dynamic changes,so that the fingered citron presents different fruit shapes.Combined with the accumulated chilling hours data,it can be found that the temperature effect is an important factor that affects the longitudinal and transverse growth of the fingered cirton before the appearance of the fingered citron flower buds.4.By observing the inner sections of flower bud and fruits of fingered citron with different accumulated chilling hours,the cytological mechanism of fruit shaping difference was analyzed.In the paraffin section of flower bud,it was found that the difference between fist(shape)and finger(shape)is manifested in the fusion of flower bud carpel,which may directly determine the type of fruit shape.5.Bioinformatics and q RT-PCR were used to analyze the differential expression of related genes in fingered citron with different accumulated chilling hours: Temperature sensitive transcription factor SPF1 and transcription factors SQUA and PI responded to low temperature in fingered citron.Meanwile,the expression pattern of MYB305 relates to flower development was induced by low temperature.The pistil development of fingered citron may end ahead of time under high temperature.YABBY5 may respond to temperature after flowering.The flowering genes V1-N3,FLC and FT induced by low temperature may promote the flowering of fingered citron.In summary,the accumulated chilling hours differed at the early stage of pistil differentiation.On the one hand,it will regulate the expression of CRC and in the differences fusion in the flower bud carpel.On the other hand,it will also cause the difference in expressions of low temperature induced genes SPF1,YABBY5.These two will facilitate the development trend of finger-like and fist-like fruit shape.Therefore,this paper preliminary analyzes the response mechanism of temperature effect on fruit shaping in fingered citron,and confirms that the fruit shaping in fingered citron formation occurs before the rapid growth period.the fruit shaping in fingered citron occurred before the rapid growth period.