Sulfur-Induced Resistance against Pseudomonas syringae pv. actinidiae via Triggering Salicylic Acid Signaling Pathway in Kiwifruit

Abstract

Sulfur has been previously reported to modulate plant growth and exhibit significant anti-microbial activities. However, the mechanism underlying its diverse effects on plant pathogens has not been elucidated completely. The present study conducted the two-year field experiment of sulfur application to control kiwifruit canker from 2017 to 2018. For the first time, our study uncovered activation of plant disease resistance by salicylic acid after sulfur application in kiwifruit. The results indicated that when the sulfur concentration was 1.5–2.0 kg m−3, the induced effect of kiwifruit canker reached more than 70%. Meanwhile, a salicylic acid high lever was accompanied by the decline of jasmonic acid. Further analysis revealed the high expression of the defense gene, especially AcPR-1, which is a marker of the salicylic acid signaling pathway. Additionally, AcICS1, another critical gene of salicylic acid synthesis, was also highly expressed. All contributed to the synthesis of increasing salicylic acid content in kiwifruit leaves. Moreover, the first key lignin biosynthetic AcPAL gene was marked up-regulated. Thereafter, accumulation of lignin content in the kiwifruit stem and the higher deposition of lignin were visible in histochemical analysis. Moreover, the activity of the endochitinase activity of kiwifruit leaves increased significantly. We suggest that the sulfur-induced resistance against Pseudomonas syringae pv. actinidiae via salicylic activates systemic acquired resistance to enhance plant immune response in kiwifruit.

Evaluation of the Abilities of Three Kinds of Copper-Based Nanoparticles to Control Kiwifruit Bacterial Canker

“…The significant difference in control effect of the three compounds in vivo and in vitro is the result of their completely different antimicrobial mechanisms. In addition, natural and synthetic plant immunity inducers, including sulfur and benzothiadiazole, have little effect on pathogens in vitro, but effectively reduce infection in vivo by activating the systemic-acquired resistance signal transduction pathway [ 26 , 54 , 55 , 56 , 57 ]. Nanoparticles, including copper phosphate and silica nanoparticles, usually have complex resistant mechanisms for plant disease in vivo, such as regulating the expression of plant defense genes or inducing systemic-acquired resistance to enhance disease resistance [ 44 , 58 ].…”

“…Recently, many novel compounds or methods have been developed to control kiwifruit bacterial canker, including natural products [ 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 ], synthetic organic compounds [ 3 , 18 , 19 , 20 , 21 , 22 , 23 ], copper complexes [ 24 , 25 ], sulfur [ 26 ], bacteriophages [ 27 , 28 , 29 ], and other biological control agents [ 30 , 31 ]. These methods exhibited excellent control efficacies for kiwifruit bacterial canker.…”

Metabolome and Transcriptome Analysis of Sulfur-Induced Kiwifruit Stem Laccase Gene Involved in Syringyl Lignin Synthesis against Bacterial Canker

“…The current spatiotemporal control mechanism of minerals on lignin polymerization in plants, i.e., how plants coordinate, which polymerase engages in lignin monomer synthesis in what conditions, and how to lignify assembly to participate in plant disease resistance, remains largely elusive. We previously demonstrated that after sulfur treatment, 30,31 sulfur on kiwifruit in the field could reach more than 70%. The stem cell wall thickened, and the lignin content and deposition were significantly enhanced.…”

“…The stem cell wall thickened, and the lignin content and deposition were significantly enhanced. 30,31 However, regarding the bacterial diseases caused by P. syringae, no reports exist that focus on the application of sulfur for the control of such diseases and the corresponding SIR, limiting the in-depth understanding of sulfur on plant physiological functions and disease resistance mechanisms and hampering the research process on mineral nutrient element-induced disease resistance.…”

“…Based on previous studies, it has been confirmed that SIR is related to lignification in kiwifruit stems. 30,31 However, little is known about the SIR-related lignin synthesis pathway and the molecular mechanism. In this study, the lignin histological staining, deposition, monomer structure, and biosynthesis enzyme activity were identified.…”