Analysis Of The Mechanism Of H₂O₂ And NO Interaction During Tuber Dormancy Release In Potato

Potato is the fourth largest food crop in the world,which is reproduced asexually through tubers.The tuber dormancy period is very important for potato industry.When the tubers are used as seed,the long dormancy period will lead to difficult to sprouting and impact on potato cultivation.When the tubers are used as commercial potato,the early tuber sprout is resulted from short dormancy period will lead to the decrease and even waste of commodity value.Therefore,it is helpful for us to accurately control the dormancy period of tuber and ensure the safe and efficient development of potato industry by studying the mechanism of its dormancy and sprouting.The dormancy of potato tubers were influenced by hormones,genetic factors,temperature,signaling molecules and reactive oxygen species,etc.At present,the mechanism of tuber dormancy and sprouting is mainly regulated by plant hormone metabolism.Reactive oxygen species（ROS）,as metabolic by-products of plant normal life activities and stress,can accelerate plant senescence and promote seed germination.In previous studies,we screened the differentially expressed genes and proteins associated with ROS and antioxidants in transcriptome and proteome level,indicating that ROS and antioxidant systems are closely related to tuber dormancy release.However,ROS and antioxidant in regulation of tuber dormancy is still unkown.In this study,the potato cultivar“Favorita”was used as the experimental material.The dormant tubers were treated with exogenous ROS donor,hydrogen peroxide（H₂O₂）,NO donor,sodium nitroprusside（SNP）and various enzyme inhibitors.The tuber sprouting rate,hormone content and related antioxidant enzyme activity were measured.The expression of genes involved in the regulation of tuber dormancy was detected.The relationship between physiological indexes and gene expression level was analyzed.The main findings are as follows:1.Exogenous H₂O₂treatment promoted St RBOHA gene expression and increased NOX enzyme activity,thus promoting endogenous H₂O₂production.Subsequently,α-amylase activity in tuber bud was induced by H₂O₂mediated GA biosynthesis,which eventually led to tuber sprout.Whereas DPI treatment significantly inhibited NOX enzyme activity,and reduced endogenous H₂O₂production,thus,prolongled tuber dormancy period by reducing GA biosynthesis andα-amylase activity.Exogenous GA₃treatment promoted St RBOHA gene expression and increased NOX enzyme activity,thus promoting endogenous H₂O₂production,further to control tuber dormancy characteristics.2.The SOD and CAT activity in sprouting tubers were significantly higher than those in dormant tubers.Exogenous H₂O₂treatment significantly increased St CYP707A1 gene expression and decreased St NCED1 gene expression,thus inhibiting the biosynthesis of ABA by promoting its catabolism,so as to induce tuber sprouting.Compared with H₂O₂action,both NOX enzyme activity and endogenous H₂O₂production significantly decreased in exogenous ASA treatment.The H₂O₂promoted tuber dormancy by increasing the content of endogenous ABA.Exogenous ABA treatment inhibited St RBOHA gene expression and decreased NOX enzyme activity,thus inhibiting endogenous H₂O₂production,further to control tuber dormancy characteristics.3.Exogenous SNP treatment promoted expressions of St NOS-IP and St NR genes,and increased activities of NOS-like and NR,further promoted the production of endogenous NO.Subsequently,NO increased endogenous GA content by promoting GA biosynthesis and inhibited its catabolism,thereby led to tuber sprouting.Compared to SNP action,c-PTIO treatment significantly inhibited the activities of NOS-like and NR,thereby inhibiting the production of endogenous NO.NO promoted tuber dormancy by reducing endogenous GA content via inhibiting GA biosynthesis and promoting its catabolism.Exogenous GA₃treatment promoted the expression of St NOS-IP and St NR genes,increased NOS-like and NR activity,further promoted endogenous NO production.Moreover,SNP treatment increased the relative expressions of St SOD1 and St CAT1 genes,and increased the activities of SOD and CAT,further enhanced the antioxidant capacity during dormancy release of potato tubers.4.Exogenous SNP treatment promoted endogenous NO production.Subsequently,NO decreased the content of endogenous ABA via promoting ABA catabolism and inhibited its biosynthesis,thereby led to tuber sproute.c-PTIO treatment,in contrast to SNP action,significantly inhibited NOS-like and NR activity,further reduced endogenous NO production.Subsequently,NO inhibited ABA catabolism and promoted its biosynthesis,further increased the endogenous ABA content,and finally inhibited tuber dormancy.Exogenous ABA treatment inhibited St NOS-IP and St NR expression,decreased NOS-like and NR activity,further inhibited endogenous NO production,further to control tuber dormancy characteristics.5.Exogenous H₂O₂treatment promoted the production of endogenous NO,and NO enhanced the expressions of St CYP707A1 and St GA3ox1genes,further promoted ABA catabolism and GA biosynthesis,which reduced the content of ABA while increased the content of GA,further to break the balance of ABA and GA,and lead to the release of tuber dormancy.Meanwhile,SNP and NO scavenger c-PTIO had no significant effects on H₂O₂production.