Role of salicylic acid glucosyltransferase in balancing growth and defence for optimum plant fitness

Abstract

Salicylic acid (SA), an essential secondary messenger for plant defence responses, plays a role in maintaining a balance (trade‐off) between plant growth and resistance induction, but the detailed mechanism has not been explored. Because the SA mimic benzothiadiazole (BTH) is a more stable inducer of plant defence than SA after exogenous application, we analysed expression profiles of defence genes after BTH treatment to better understand SA‐mediated immune induction. Transcript levels of the salicylic acid glucosyltransferase (SAGT) gene were significantly lower in BTH‐treated Nicotiana tabacum (Nt) plants than in SA‐treated Nt control plants, suggesting that SAGT may play an important role in SA‐related host defence responses. Treatment with BTH followed by SA suppressed SAGT transcription, indicating that the inhibitory effect of BTH is not reversible. In addition, in BTH‐treated Nt and Nicotiana benthamiana (Nb) plants, an early high accumulation of SA and SA 2‐O‐β‐d‐glucoside was only transient compared to the control. This observation agreed well with the finding that SAGT‐overexpressing (OE) Nb lines contained less SA and jasmonic acid (JA) than in the Nb plants. When inoculated with a virus, the OE Nb plants showed more severe symptoms and accumulated higher levels of virus, while resistance increased in SAGT‐silenced (IR) Nb plants. In addition, the IR plants restricted bacterial spread to the inoculated leaves. After the BTH treatment, OE Nb plants were slightly larger than the Nb plants. These results together indicate that SAGT has a pivotal role in the balance between plant growth and SA/JA‐mediated defence for optimum plant fitness.

Overexpression of Salicylic Acid Carboxyl Methyltransferase (CsSAMT1) Enhances Tolerance to Huanglongbing Disease in Wanjincheng Orange (Citrus sinensis (L.) Osbeck)

“…The overexpression of the UGT74F1 homologous gene AtSGT1 in Arabidopsis reduced SA accumulation and increased plant susceptibility to Pseudomonas syringae [ 39 ]. In tobacco, overexpression of SAGT also reduced SA levels and increased plant susceptibility to the cucumber mosaic virus strain Y whilst RNAi-mediated silencing of SAGT enhanced resistance [ 40 ]. These results suggest that the repression of CsUGT74F1 expression in CsSAMT1 overexpressing transgenic plants enhances tolerance to HLB by elevating SA levels.…”

A Ubiquitously Expressed UDP-Glucosyltransferase, UGT74J1, Controls Basal Salicylic Acid Levels in Rice

“…The ugt74f1 and ugt74f2 Arabidopsis single mutants show reduced SAG and SGE levels, respectively, and the ugt74f1 mutant also shows an increased SA level [ 19 ]. Overexpression of SAGT in Nicotiana benthamiana results in decreased SA and increased SAG levels [ 26 ]. The rice OsSGT1 is a probenazole (PBZ)-inducible gene, and its knock-down mutants exhibit a reduced SAG level under PBZ treatment [ 25 ].…”

Bacterial Compound N,N-Dimethylhexadecylamine Modulates Expression of Iron Deficiency and Defense Response Genes in Medicago truncatula Independently of the Jasmonic Acid Pathway

“…It is proposed that plants maintain an energetic balance between growth and defense [61]. In this way, the stimulation of defense pathways has a detrimental effect on growth [62,63]. Other bacterial VOCs, such as 2,3-butanediol, have the ability to activate both SAR and ISR defense pathways simultaneously with plant growth promotion [64], as DMHDA did.…”