S-Glycoprotein-Like Protein Regulates Defense Responses in Nicotiana Plants against Ralstonia solanacearum      

Abstract

RsRGA4 (for Ralstonia solanacearum-responsive gene A4) encodes a polypeptide similar to S-locus glycoprotein (SGP) from Brassica rapa and SGP-like proteins from Ipomoea trifida and Medicago truncatula. Therefore, we designated RsRGA4 as NtSGLP (for Nicotiana tabacum SGP-like protein) and NbSGLP (its Nicotiana benthamiana ortholog). NbSGLP is expressed in root, leaf, petal, gynoecium, and stamen. Expression of NbSGLP was strongly induced by inoculation with an avirulent strain of R. solanacearum (Rs8107) and slightly enhanced by inoculation with virulent R. solanacearum (RsOE1-1). Expression of NbSGLP was induced by inoculation with an hrpY-deficient mutant of RsOE1-1 and Rs8107. Expression was also induced by aminocyclopropane carboxylic acid and salicylic acid. Virus-induced gene silencing of NbSGLP enhanced the growth of Rs8107. Growth of RsOE1-1 and appearance of wilt symptoms were also accelerated in silenced plants. Expression of PR-1a and EREBP was reduced, and markers for basal defense, such as callose deposition and reduced vascular flow, were compromised in NbSGLP-silenced plants. Moreover, growth of Pseudomonas cichorii, Pseudomonas syringae pv tabaci, and P. syringae pv mellea was also enhanced in the silenced plants. On the other hand, silencing of NbSGLP did not interfere with the appearance of the hypersensitive response. NbSGLP was secreted in a signal peptide-dependent manner. Agrobacterium tumefaciens-mediated expression of NbSGLP induced PR-1a and EREBP expression, callose deposition, and reduced vascular flow. NbSGLP-induced callose deposition and reduced vascular flow were not observed in salicylic acid-deficient N. benthamiana NahG plants. Taken together, SGLP might have a role in the induction of basal defense in Nicotiana plants.

Virus-induced gene silencing and its application in plant functional genomics

“…In addition, the roles of SGT1 and SlALC1, two key genes in the coronatine/jasmonate (JA) pathway, and inducible NO synthase (iNOS) in resistance against P. syringae have been uncovered [107]. In tobacco plants, the important roles of NbHSP90c-1, NbHSP70c-1, WIPK, and SIPK genes in non-host resistance to P. cichorii, and SGLP in resistance against Ralstonia solanacearum, have been demonstrated by VIGS [108][109][110]. In a study searching for genes required for defense responses against Xanthomonas campestris in plants, Bs4, SGT1, CaCYP450A, CaRING1, SlMKK2 and SlMPK2 genes have been characterized [111][112][113][114][115].…”

Novel type of adenylyl cyclase participates in tabtoxinine-β-lactam-induced cell death and occurrence of wildfire disease inNicotiana benthamiana

“…26 P. syringae pv tabaci 6605 was cultured in PY medium containing 20 µg/ mL rifampicin. 27 Purification of TβL was performed according to the method described by Tomas et al 28 Bacterial suspension, l-methionine sulfoximine (MSX; Funakoshi) and TβL were infiltrated into N. benthamiana leaves as described previously. 9 Isolation of RNA and cDNA synthesis Total RNA was isolated from N. benthamiana leaves with RNAiso (Takara), and RNA samples were treated with DNase I (RNase-free; Takara) to degrade contaminating genomic DNA as described previously.…”

Molecular chaperons and co-chaperons, Hsp90, RAR1, and SGT1 negatively regulate bacterial wilt disease caused byRalstonia solanacearuminNicotiana benthamiana

“…13 Ralstonia solanacearum strain OE1-1 and the corresponding hrpY (encoding Hrp pilus)-mutant of R. solanacearum strain OE1-1 was cultured in PY medium containing 20 mg/mL rifampicin or 20 mg/mL kanamycin, respectively. 12 Bacterial suspension were infiltrated into N. benthamiana leaves as described previously. 13 …”

“…7 We previously reported that cellular components, such as asparagine-rich protein, S-glycoprotein-like protein and translationally controlled tumor protein, have important role in regulation of plant defenses against R. solanacearum. [10][11][12] In addition, our previous report showed that molecular chaperon, Nbshsp17, has a crucial role in regulation of plant defenses, suggesting involvement of molecular chaperons and co-chaperons in plant and R. solanacearum interaction. 13 In this study, we focused on Hsp90, RAR1 and SGT1.…”