Activated Expression of Rice DMR6-like Gene OsS3H Partially Explores the Susceptibility to Bacterial Leaf Streak Mediated by Knock-Out OsF3H04g

Abstract

Downy Mildew Resistance 6-like (DMR6-like) genes are identified as salicylic acid (SA) hydroxylases and negative regulators of plant immunity. Previously, we identified two rice DMR6-like genes, OsF3H03g, and OsF3H04g, that act as susceptible targets of transcription activator-like effectors (TALEs) from Xanthomonas oryzae pv. oryzicola (Xoc), which causes bacterial leaf streak (BLS) in rice. Furthermore, all four homologs of rice DMR6-like proteins were identified to predominantly carry the enzyme activity of SA 5-hydroxylase (S5H), negatively regulate rice broad-spectrum resistance, and cause the loss of function of these OsDMR6s, leading to increased resistance to rice blast and bacterial blight (BB). Here, we curiously found that an OsF3H04g knock-out mutant created by T-DNA insertion, osf3h04g, was remarkedly susceptible to BLS and BB and showed an extreme reduction in SA content. OsF3H04g knock-out rice lines produced by gene-editing were mildly susceptible to BLS and reduced content of SA. To explore the susceptibility mechanism in OsF3H04g loss-of-function rice lines, transcriptome sequencing revealed that another homolog, OsS3H, had induced expression in the loss-of-function OsF3H04g rice lines. Furthermore, we confirmed that a great induction of OsS3H downstream and genomically adjacent to OsF3H04g in osf3h04g was primarily related to the inserted T-DNA carrying quadruple enhancer elements of 35S, while a slight induction was caused by an unknown mechanism in gene-editing lines. Then, we found that the overexpression of OsS3H increased rice susceptibility to BLS, while gene-editing mediated the loss-of-function OsS3H enhanced rice resistance to BLS. However, the knock-out of both OsF3H04g and OsS3H by gene-editing only neutralized rice resistance to BLS. Thus, we concluded that the knock-out of OsF3H04g activated the expression of the OsS3H, partially participating in the susceptibility to BLS in rice.

Comparative transcriptomic profiling of the two-stage response of rice to Xanthomonas oryzae pv. oryzicola interaction with two different pathogenic strains

“…ZH11 leaves inoculated with HGA4 and RS105 at 12 h and 3 d were collected for RNA-seq, and uninoculated leaves were used as controls. As previously reported [ 16 ], total RNA was isolated from rice leaves using TRI reagent (Sigma‒Aldrich, USA). Triplicate RNA samples were sequenced with BGISEQ-500 by the Beijing Genomic Institution (Shenzhen, China).…”

“…Modification of DR gene expression can improve rice resistance to Xoc. In addition to singleton DR genes, some DR gene families, such as OsWRKY45-1 and OsWRKY45-2 [ 12 ], the polygalacturonase inhibiting protein genes OsPGIP1 and OsPGIP4 [ 13 ], and the salicylic acid (SA) metabolic enzyme family OsF3H03g , OsF3H04g , and OsS3H [ 14 – 16 ], have also been reported to be involved in BLS resistance. Some transcription modules, such as OsHsfB4d-OsHsp18.0-CI [ 17 ] and OsASR6-OsCIPK15 [ 18 ], are also involved in BLS resistance.…”

OsACA9, an Autoinhibited Ca2+-ATPase, Synergically Regulates Disease Resistance and Leaf Senescence in Rice

“…The bacterial colony was suspended in sterile distilled water at an optical density of OD 600 = 1.0 and immediately used for inoculation. At the tillering stage, the leaf tip clipping method [86] was used for inoculation of Xoo, and the non-needle syringe injection method [87] was used for inoculation of Xoc. Lesions on the inoculated leaves were measured for the evaluation of resistance 2 weeks after inoculation.…”