Study On The Mechanism Of Stem Dwarfing And Elongation Of Inflorescence In Peanut Induced By Overexpression Of AhphyA

Plant architecture mainly refers to the development of stems,leaves,branches and flowers,including plant height,leaf shape,branches and inflorescence.Plant height,an important agronomic trait,is one of the key research fields.Suitable plant height can improve the utilization efficiency of light,thus contributing to the accumulation of organic substance and increasing yield finally.However,stem height of crops is too high to prone to lodging,resulting in imbalance of vegetative and reproductive growth.Therefore,chemical control is usually used to inhibit stem height of crops to increase yield in agricultural production.However,chemical control is easy to cause environmental pollution.Inflorescence is a metamorphosed branch with flowers,also called a reproductive or spray,and the inflorescence affects crop yield.The inflorescence axis of LH14 is very short,bearing three fascicled flowers.Our previous study found that the overexpression of phyA in peanut caused the shorter main stem and the longer inflorescence axis with the increased number of flowers.The previous results showed that GA content in main stem decreased significantly while GA and IAA content in inflorescence axis increased significantly.In order to further investigate the mechanism of phyA overexpression causing main stem dwarfing and inflorescence axis elongation,the role of GA was explored through exogenous spraying of GA and IAA and their inhibitors,and the genes involved in this process was further explored.The present study not only analyzed the tissue-specific regulation mechanism of phyA on the main stem height and the length of inflorescence axis,but also provided a strategy for obtaining ideal plant height by biotechnology in agricultural production.The main results are as follows:1.The changes of plant height during the whole growth period and pod traits of OEAhphyA lines were investigated.At the seedling age of 30-60 days,there was no obvious difference about the plant height and lateral branch length of between OEAhphyA lines and LH14.After 60 days,the main stem and lateral branch growth of the three OEAhphyA lines were slowed down,which were significantly lower than those of LH14 at 120 d.In addition to plant height,pod and kernel weight of OEAhphyA lines decreased markedly,at the same time,oleic acid and crude protein content of OEAhphyA lines also decreased significantly,while linoleic acid and sucrose content increased remarkably.2.In order to explore whether the regulation of phyA overexpression on peanut main stem is related to GA content,150μM GA₃ and 150μM PP333,a GA inhibitor,were sprayed on the leaves of 35-day seedlings of LH14 and OEAhphyA lines,respectively.The results showed that the growth of main stem of OEAhphyA and LH14 was significantly promoted by GA₃,while markedly inhibited by PP333.After GA₃ and PP333 treatments,there was no significant difference in the height of main stem of OEAhphyA lines and LH14.These results indicated that GA may be the main hormone involved in the regulation of plant height of peanut by phyA overexpression.3.In order to analyze the role of gibberellin and auxin in promoting the rachis elongation of OEAhphyA lines,foliar application of 150μM GA₃,50 mg/l IAA and the mix of 150μM GA₃and 50 mg/l IAA were performed on 30-day seedlings of LH14,respectively.The results showed that the length of inflorescence axis was not changed after IAA treatment,whereas which was significantly increased by GA₃ alone application.Furthermore,the mix of GA₃ and IAA significantly increased the number and length of elongated rachis.These results indicated that the elongation of the inflorescence axis was mainly regulated by the increase of GA content in the inflorescence axis,and IAA promoted this process.4.To further investigate the role of gibberellin and auxin in promoting axial elongation of OEAhphyA lines,30-day seedlings of OEAhphyA lines（6A12 and 6B9）were sprayed with 100μM PP333（GA synthesis inhibitors）,100μM Kyn（IAA synthesis inhibitors）and the mixture of100μM PP333 and 100μM Kyn,respectively.The results showed that Kyn could significantly shorten the length of inflorescence axis but could not inhibit the elongation of inflorescence axis.The length of inflorescence axis of OEAhphyA was reduced to the level of LH14 after PP333alone or PP333 mixed with Kyn.These results illustrated that the elongation of inflorescence axis in OEAhphyA lines might be resulted from accumulation of GA in inflorescence axis due to overexpression of phyA,and IAA could promote inflorescence axis elongation.5.To explore which member of the key gene families of GA synthesis and metabolism in peanut is involved in the process regulated by AhphyA,the main stem dwarfing and inflorescence axis elongation,the Ah GA20ox,Ah GA3ox and Ah GA2ox gene families were analyzed by bioinformatics.A total of 15 Ah GA20ox,5 Ah GA3ox and 16 Ah GA2ox family members were identified in peanut.The expression levels of Ah GA20ox,Ah GA3ox and Ah GA2ox gene family members in the main stem and inflorescence axis of peanut were detected by q RT-PCR.The results showed that 20 genes were expressed in the main stem and inflorescence,while the expression patterns were different.Interestingly,the expression levels of Ah GA20ox12/Ah GA20ox15 and Ah GA3ox4/Ah GA3ox5 in the main stem of LH14 were significantly higher than those of 6A12 and 6B9,while the expression levels of these two genes in the inflorescence axis of LH14 were significantly lower than those of 6A12 and 6B9,suggesting that,Ah GA20ox12/Ah GA20ox15 and Ah GA3ox4/Ah GA3ox5 may be involved in main stem dwarfing and inflorescence axis elongation regulated by AhphyA.