Functional Characterization Of PtrIAA12 Regulating Growth And Response To Drough Stress In Populus Trichocarpa

Trees are not only important raw materials for industrial production such as building,biomass fuel,and papermaking,and most of the approximately 56 billion tons of CO2 that terrestrial plants fix each year are also stored in wood.Therefore,trees have important ecological and economic value.In the current situation of increasingly severe ecological security issues and depletion of timber resources,it is imperative to accelerate the research on the growth and development and the response mechanism of abiotic stress in tree.The AUX/IAA gene encodes the core auxin signal transduction protein,which plays an important role in plant growth and development and response to stress.Among them,IAA12 can regulate root and leaf development and response to drought stress in herbs.However,so far,there is no report on the function of IAA12 gene in woody plants.In order to explore the function of IAA12 in woody plants,this study used Populus trichocarpa,a woody model plant,as the research material,through bioinformatics,yeast hybridization experiment,genetic transformation and other methods.The expression characteristics and biological functions in development as well as drought stress response of PtrIAA12 were analyzed.It was found that the expression level of PtrIAA12 in the primary stems and leaves of Populus trichocarpa was higher,and the expression level in each tissue was significantly reduced after drought stress through qRT-PCR.Amino acid sequence analysis showed that PtrIAA12 has the characteristic motifs of AUX/IAA family proteins-EAR,VGWPP motif and PB1 domain.The leaf experiment of transiently transformed tobacco(Nicotiana tabacum)found that PtrIAA12 was localized in the nucleus,and the transcription activation experiment showed that PtrIAA12 has transcriptional repressive activity.Agrobacterium(Agrobacterium tumefacien)infection method was used to obtain PtrIAA12 overexpression and gene function inhibited ▽ptrIAA12 overexpression transgenic Populus trichocarpa(PtrIAA12-OE and ▽PtrIAA12-OE).It is observed that PtrIAA12 can inhibit the growth of Populus stems.Staining observation of paraffin sections of stems showed that PtrIAA12 can reduce the peak of cambium activity and delay the decline of cambium division activity.Scanning electron microscope observations show that PtrIAA12 can inhibit secondary wall deposition.The analysis of root development showed that PtrIAA12 could promote the formation and growth of adventitious roots and inhibit the formation and growth of lateral roots.Observation of root basal section showed that PtrIAA12 can promote the thickening and growth of the main root,promote the division of root cambium,and inhibit the thickening and growth of ductal cells.The analysis of leaf traits showed that PtrIAA12 can promote leaf growth,increase the angle within the leaf base,promote the formation of stomata,and inhibit the growth of guard cells.The analysis of petiole traits showed that PtrIAA12 can promote petiole growth.The analysis of traits under drought stress showed that PtrIAA12 could inhibit the drought tolerance of Populus tomentosa.Combined with the ability of PtrIAA12 to respond to drought stress and the phenotypic differences of each plant,it can be explained that PtrIAA12 can down-regulate the expression level in response to drought stress,thereby inhibiting the growth and stomata formation of new leaves,reducing the transpiration of new leaves,and ultimately improving the growth and development mode of plants.More suitable for arid environment.Many phenotypic change trends of VPtrIAA12-OE are opposite to those of PtrIAA12-OE,which shows that it is feasible to cultivate its gene function defect by using a protein with no transcriptional inhibitory activity with mutant EAR motif to compete with the original AUX/IAA.of.In summary,PtrIAA12 exhibits multiple functions in Populus trichocarpa.It can not only inhibit stem growth,promote leaf growth,promote adventitious root formation and growth,inhibit lateral root formation and development,and maintain cambium division activity,but also through regulating stomata density affects the drought tolerance of Populus trichocarpa.This can deepen the understanding of the functions of auxin and AUX/IAA in the growth and development of woody plants and in response to drought stress.Among them,▽PtrIAA12-OE exhibits excellent characteristics of faster growth and stronger drought tolerance,which can provide a reference for the cultivation of forest trees.