| The auxin response factor(ARF)belongs to a multi-gene family,of which AtARFl can affect plant flowering,stamen development,flower abscission and fruit cracking and root growth.Most of the existing researches were based on herbs,and their function in woody plants is rarely studied.Trichoderma is recognized as an environmentally friendly biocontrol factor in the world.It not only has a potential role in soil remediation,but also promoting plant growth and has a defensive effect against various plant diseases.In this study,ARF1 overexpression tissue culture seedlings of Shanxin poplar were used as test materials,the wild seedling was used as contrast.The endogenous hormone contents changes and different expression of key genes in hormone signal transduction pathways related to adventitious root growth and resistance of two kinds of tissue culture seedlings were analyzed after inoculation with Trichoderma(T),Alternaria alternata(A)and mix inoculation(TA)for 48 hours.Thus,it reveals the regulation mode of which Trichoderma promotes the growth of transgenic Shanxin poplar and improves its resistance to pathogenic.The main findings are as follows:1.The PodaARFl-H and PodaARFl-InR plants are cultured.It found that ARF1 overexpression could accelerate the growth of Shanxin poplar,and it could increase the number of adventitious roots obviously,so it is beneficial to absorb nutrients,enhance stability,store and synthesize organic matter.However,inhibiting the expression of ARF1,the growth of Shanxin poplar was inhibited and the number of adventitious roots significantly reduces.2.The determination of hormone content showed that the contents of IAA,JA,and SA in PodaARF1-H are generally increased compared with Poda-W,and the hormone content in the treatment group of PodaARF1-H plants changed greatly.Which indicating that overexpression of ARF1 could increase the sensitivity of Shanxin poplar to external stimuli and make a quick defense.The contents of IAA,JA,and SA in three treatment groups of Poda-W and PodaARFl-H tissue culture plants were generally improved.It indicated the Trichoderma in the rhizosphere and A.alternata on leaves can promote the growth of Shanxin poplar and improve its resistance in 48 hours.3.The result of leaf tissue histochemical staining showed that the color of PodaARF1-H leaf was lighter than that of Poda-W in NBT and DAB,indicating that overexpression of ARF1 in Shanxin poplar could improve the antioxidant capacity by reducing the accumulation of.O2-and H2O2 in the plant.In Evans Blue staining,the color of PodaARF1-H was darker than that of Poda-W,indicating that overexpression of ARF1 can increase the sensitivity of the plant to external stimuli.In addition,inoculation of Trichoderma in the roots of Shanxin poplar or functional leaf inoculation with pathogenic bacteria at the initial stage enhanced the plant defense response.4.Poda-W had irregular patterns of gene expression patterns in shoot tips,treated functional leaves,and roots in the three treatment groups.In the shoot tips of the PodaARF1-H,most of the related genes in the T group were up-regulated in IAA,JA and SA signal transduction pathways,but the majority genes were down-regulated in A group of JA and S A transduction pathways;the most of JA and S A related genes in the treated leaf and root were down-regulated in the T group,while all genes in group A were significantly up-regulated.This indicates that in a short period of time the expression of ARF1 changed the gne expression pattern in plants,and increase the sensitivity of Sanxin poplar to response to Trichoderma and A.alternate.In addition,PodaARF1-H tissue culture seedlings are more sensitive to A.alternate.5.After transplanting Shanxin poplar to the soil,it was found that Trichoderma can effectively increase plant height and leaf number,and can resist injury caused by A.alternate. |
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