Growth And Development Characteristics Of CodA Transgenic Wheat And Its Response To Drought And High Temperature Stress

With the increase of global temperature and the decrease of available water resources,drought and high temperature stress have become one of the main factors restricting wheat yield.In some areas,the adverse effects of high temperature and drought on crop productivity will also increase with the deterioration of climate.A comprehensive understanding of the effects of drought and high temperature stress is conducive to timely and positive response to climate change,so as to reduce the impact of climate change on crop production.Under natural conditions,drought stress and high temperature stress have seriously affected the growth and development,even production of wheat.Glycinebetaine?GB?is a quaternary ammonium salt compound,which widely exists in bacteria,plants and mammals.Under abiotic stress,GB can increase the water retention capacity of plant cells,improve their tolerance to various abiotic stresses and maintain their normal physiological life process.The codA is one of the important genes for GB synthesis,and its research in wheat is less.In this study,the codA transgenic wheat plants were used to study the functions of GB on wheat development and on drought and high temperature resistance.The results are as follows:?1?Under normal growth condition,heterologous overexpression of the codA gene can promote the growth and development,confer an early heading phenotype as well as increase the plant height and ear length in transgenic wheat plants.?2?After drought and drought and high temperature combined-stress,although the growth of both transgenic and wild-type wheat was severely inhibited,which exhibited the growth retardation and wilting phenotype,the growth inhibition and wilting degree of transgenic plants were lower than those of wild-type plants.?3?Under long term drought stress,the heading time of transgenic wheat plants with codA is earlier than that under normal growth condition,which indicates that GB may play an important role in coordinating the growth and stress resistance of wheat.?4?After drought stress treatment,both transgenic and wild-type wheat leaves showed a obvious decrease in chlorophyll content,and an significant increase in the content of superoxide anion radical?O₂·^-?and malonaldehyde?MDA?.However,the chlorophyll content in leaves of codA-transgenic wheat was still higher than that of wild-type wheat,wherase the content of O₂·^- and MDA was lower than that in wild-type wheat,indicating that GB can mitigate the damage of drought stress in transgenic wheat plants.?5?Under simulated drought treatment,although the Ca²⁺influx speed in the main roots of transgenic wheat and wild-type wheat was increased,the Ca²⁺influx speed of codA-transgenic wheat was significantly faster than that of wild-type wheat,indicating that GB plays an important regulatory role in the process of Ca²⁺transport under drought stress.?6?After drought and drought and high temperature combined-stress,the photosystem ??PS??activity was decreased in all wheat plants.However,compared with wild-type wheat plants,the codA-transgenic wheat plants still maintained the higher PS? activity,indicating that GB could mitigate the damage of stress to PS?,thereby improving the resistance of transgenic wheat to high temperature and drought stress.