Sugar flux and signaling in plant–microbe interactions Bezrutczyk, Margaret; Yang, Jungil; Eom, Joon‐Seob ...
The Plant journal : for cell and molecular biology,
February 2018, Letnik:
93, Številka:
4
Journal Article
Recenzirano
Odprti dostop
Summary
Plant breeders have developed crop plants that are resistant to pests, but the continual evolution of pathogens creates the need to iteratively develop new control strategies. Molecular tools ...have allowed us to gain deep insights into disease responses, allowing for more efficient, rational engineering of crops that are more robust or resistant to a greater number of pathogen variants. Here we describe the roles of SWEET and STP transporters, membrane proteins that mediate transport of sugars across the plasma membrane. We discuss how these transporters may enhance or restrict disease through controlling the level of nutrients provided to pathogens and whether the transporters play a role in sugar signaling for disease resistance. This review indicates open questions that require further research and proposes the use of genome editing technologies for engineering disease resistance.
Significance Statement
Sugar efflux transporters play critical roles in plants pathogen interactions. Sugars released by them either feed the pathogens or prime defense.
Blight-resistant rice lines are the most effective solution for bacterial blight, caused by Xanthomonas oryzae pv. oryzae (Xoo). Key resistance mechanisms involve SWEET genes as susceptibility ...factors. Bacterial transcription activator-like (TAL) effectors bind to effector-binding elements (EBEs) in SWEET gene promoters and induce SWEET genes. EBE variants that cannot be recognized by TAL effectors abrogate induction, causing resistance. Here we describe a diagnostic kit to enable analysis of bacterial blight in the field and identification of suitable resistant lines. Specifically, we include a SWEET promoter database, RT-PCR primers for detecting SWEET induction, engineered reporter rice lines to visualize SWEET protein accumulation and knock-out rice lines to identify virulence mechanisms in bacterial isolates. We also developed CRISPR-Cas9 genome-edited Kitaake rice to evaluate the efficacy of EBE mutations in resistance, software to predict the optimal resistance gene set for a specific geographic region, and two resistant 'mega' rice lines that will empower farmers to plant lines that are most likely to resist rice blight.
Biotic stresses, including diseases, severely affect rice production, compromising producers' ability to meet increasing global consumption. Understanding quantitative responses for resistance to ...diverse pathogens can guide development of reliable molecular markers, which, combined with advanced backcross populations, can accelerate the production of more resistant varieties. A candidate gene (CG) approach was used to accumulate different disease QTL from Moroberekan, a blast-resistant rice variety, into Vandana, a drought-tolerant variety. The advanced backcross progeny were evaluated for resistance to blast and tolerance to drought at five sites in India and the Philippines. Gene-based markers were designed to determine introgression of Moroberekan alleles for 11 CGs into the progeny. Six CGs, coding for chitinase, HSP90, oxalate oxidase, germin-like proteins, peroxidase and thaumatin-like protein, and 21 SSR markers were significantly associated with resistance to blast across screening sites. Multiple lines with different combinations, classes and numbers of CGs were associated with significant levels of race non-specific resistance to rice blast and sheath blight. Overall, the level of resistance effective in multiple locations was proportional to the number of CG alleles accumulated in advanced breeding lines. These disease resistant lines maintained tolerance to drought stress at the reproductive stage under blast disease pressure.
Rice bacterial blight (BB) caused by Xanthomonas oryzae pv. oryzae (Xoo) implies substantial yield loss to rice. In times of climate change, increasing temperatures are observed and further ...acceleration is expected worldwide. Increasing temperature often turns into inhibition of host plant defense to pathogens. Recently, a reduced resistance in rice IRBB4 carrying Xa4, but an increase in resistance in IRBB7 carrying Xa7 resistance by increasing temperature has been reported. Influence of high temperature on both R genes (Xa4+Xa7) combined in IRBB67 was analyzed under growth chamber conditions and transcriptomic analysis performed. The pyramided line IRBB67 showed no differences in lesion length between both temperature regimes, demonstrating that non-effectiveness of Xa4 at high temperature did not affect IRBB67 resistance. Moreover, Xa4 complements Xa7 resistance with no Xoo spread in planta beyond the symptomatic area under both temperature regimes in IRBB67. Time course transcriptomic analysis revealed that temperature enhanced IRBB67 resistance to combined heat and Xoo. Our findings highlight altered cellular compartments and point at a role of the cell wall involved in Xoo resistance and heat stress tolerance in both susceptible (IR24) and the resistant (IRBB67) NILs. Interestingly, up-regulation of trehalose-6-phosphatase gene and low affinity cation transporter in IRBB67 suggest that IRBB67 maintained a certain homeostasis under high temperature which may have enhanced its resistance. The interplay of both heat stress and Xoo responses as determined by up-regulated and down-regulated genes demonstrates how resistant plants cope with combined biotic and abiotic stresses.
Plant disease is a major challenge to agriculture worldwide, and it is exacerbated by abiotic environmental factors. During some plant-pathogen interactions, heat stress allows pathogens to overcome ...host resistance, a phenomenon which could severely impact crop productivity considering the global warming trends associated with climate change. Despite the importance of this phenomenon, little is known about the underlying molecular mechanisms. To better understand host plant responses during simultaneous heat and pathogen stress, we conducted a transcriptomics experiment for rice plants (cultivar IRBB61) containing Xa7, a bacterial blight disease resistance (R) gene, that were infected with Xanthomonas oryzae, the bacterial blight pathogen of rice, during high temperature stress. Xa7-mediated resistance is unusual relative to resistance mediated by other R genes in that it functions better at high temperatures. Using RNA-Seq technology, we identified 8,499 differentially expressed genes as temperature responsive in rice cultivar IRBB61 experiencing susceptible and resistant interactions across three time points. Notably, genes in the plant hormone abscisic acid biosynthesis and response pathways were up-regulated by high temperature in both mock-treated plants and plants experiencing a susceptible interaction and were suppressed by high temperature in plants exhibiting Xa7-mediated resistance. Genes responsive to salicylic acid, an important plant hormone for disease resistance, were down-regulated by high temperature during both the susceptible and resistant interactions, suggesting that enhanced Xa7-mediated resistance at high temperature is not dependent on salicylic acid signaling. A DNA sequence motif similar to known abscisic acid-responsive cis-regulatory elements was identified in the promoter region upstream of genes up-regulated in susceptible but down-regulated in resistant interactions. The results of our study suggest that the plant hormone abscisic acid is an important node for cross-talk between plant transcriptional response pathways to high temperature stress and pathogen attack. Genes in this pathway represent an important focus for future study to determine how plants evolved to deal with simultaneous abiotic and biotic stresses.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Basmati is a premium quality rice, famous for its aroma, fine grain, and excellent cooking qualities. However, it is highly susceptible to bacterial leaf blight (BLB). To develop BLB resistant ...Basmati rice varieties, we transferred three (03) BLB resistance genes namely
Xa4
,
xa5
,
Xa21
from a coarse yet BLB-resistant variety, IRBB57, developed by International Rice Research Institute into fine-quality rice variety, Super Basmati, through marker-assisted breeding. The background parent genome was recovered performing several backcrosses using Super Basmati as a recurrent parent to restore the bona fide Basmati character. The introgression of BLB resistance genes was followed by foreground selection using DNA-markers tightly linked with BLB resistance genes. The recovery of the Basmati parent genome (Background Selection) was determined using two different marker systems. Simple Sequence Repeats and Single Nucleotide Polymorphism. Several Super Basmati Introgressed (SBIL) lines with the individual as well as different BLB resistance gene combinations were developed. The stable representative SBILs from single, double, and triple gene combinations showing > 90% parent genome recovery were further studied for different attributes particularly to determine their degree of tolerance to the bacterial blight that was studied at two different locations—Philippines and Pakistan. We observed that SBILs carrying a combination of
xa5
+
Xa21
and
Xa4
+
xa5
+
Xa21
conferred broad-scale resistance against both the highly virulent Pakistani and Philippines
Xanthomonas oryzae
pv.
oryzae
strains. The marker-aided background selection coupled with stringent phenotypic selection as well as foreground selection using DNA markers tightly linked with grain quality ensured that SBILs possess the bona fide Basmati character. The performance of key agronomic traits in selected SBILs was comparable with the recurrent parent with no significant agronomic or yield penalty associated with incorporation of the resistance genes, confirming the linkage drag has been minimized. Therefore, in addition to sustaining Basmati rice yield against BLB, the SBILs developed in this study may represent a useful resource for transferring resistance to BLB-susceptible rice varieties.
A 1D/2D genome-wide association study strategy was adopted to investigate the genetic systems underlying the reciprocal adaptation of rice (Oryza sativa) and its bacterial pathogen, Xanthomonas ...oryzae pv. oryzae (Xoo) using the whole-genome sequencing and large-scale phenotyping data of 701 rice accessions and 23 diverse Xoo strains. Forty-seven Xoo virulence-related genes and 318 rice quantitative resistance genes (QR-genes) mainly located in 41 genomic regions, and genome-wide interactions between the detected virulence-related genes and QR genes were identified, including well-known resistance genes/virulence genes plus many previously uncharacterized ones. The relationship between rice and Xoo was characterized by strong differentiation among Xoo races corresponding to the subspecific differentiation of rice, by strong shifts toward increased resistance/virulence of rice/Xoo populations and by rich genetic diversity at the detected rice QR-genes and Xoo virulence genes, and by genome-wide interactions between many rice QR-genes and Xoo virulence genes in a multiple-to-multiple manner, presumably resulting either from direct protein-protein interactions or from genetic epistasis. The observed complex genetic interaction system between rice and Xoo likely exists in other crop-pathogen systems that would maintain high levels of diversity at their QR-loci/virulence-loci, resulting in dynamic coevolutionary consequences during their reciprocal adaptation.
Sheath blight caused by
Rhizoctonia solani
is a major rice disease worldwide and causes serious yield losses. To identify quantitative differences in disease development, four inoculum sources, viz. ...typha bit, maize-sand meal medium, rice grain-rice hull and tooth pick were evaluated against twelve rice genotypes using artificial inoculation conditions for 2 years. Relative lesion height (RLH) was measured at 7, 14 and 21 days after inoculation. Disease incidence was recorded at 21 days post inoculation. Inoculum sources significantly affected disease development. Typha bit inoculation showed the highest RLH (55.1%) as well as area under disease progress curve (AUDPC) (828.8), while the lowest disease development occurred with tooth pick inoculum (RLH 47.1% and AUDPC 626.8). The interaction between genotypes and inoculum sources was significant. Rice varieties Tetep and Taducan showed the lower RLH and AUDPC as compared to all other genotypes with different inoculum sources. These results provide a basis to design methods of evaluation for sheath blight resistance with high precision in rice genotypes.
Bacterial blight of rice is an important disease in Asia and Africa. The pathogen, Xanthomonas oryzae pv. oryzae (Xoo), secretes one or more of six known transcription-activator-like effectors ...(TALes) that bind specific promoter sequences and induce, at minimum, one of the three host sucrose transporter genes SWEET11, SWEET13 and SWEET14, the expression of which is required for disease susceptibility. We used CRISPR-Cas9-mediated genome editing to introduce mutations in all three SWEET gene promoters. Editing was further informed by sequence analyses of TALe genes in 63 Xoo strains, which revealed multiple TALe variants for SWEET13 alleles. Mutations were also created in SWEET14, which is also targeted by two TALes from an African Xoo lineage. A total of five promoter mutations were simultaneously introduced into the rice line Kitaake and the elite mega varieties IR64 and Ciherang-Sub1. Paddy trials showed that genome-edited SWEET promoters endow rice lines with robust, broad-spectrum resistance.
As molecular interactions of plants with N2-fixing endophytes are largely uncharacterized, we investigated whether the common signaling pathway (CSP) shared by root nodule symbioses (RNS) and ...arbuscular mycorrhizal (AM) symbioses may have been recruited for the endophytic Azoarcus sp.–rice (Oryza sativa) interaction, and combined this investigation with global approaches to characterize rice root responses to endophytic colonization.
Putative homologs of genes required for the CSP were analyzed for their putative role in endophytic colonization. Proteomic and suppressive subtractive hybridization (SSH) approaches were also applied, and a comparison of defense-related processes was carried out by setting up a pathosystem for flooded roots with Xanthomonas oryzae pv. oryzae strain PXO99 (Xoo).
All tested genes were expressed in rice roots seedlings but not induced upon Azoarcus sp. inoculation, and the oscyclops and oscastor mutants were not impaired in endophytic colonization. Global approaches highlighted changes in rice metabolic activity and Ca2+-dependent signaling in roots colonized by endophytes, including some stress proteins. Marker genes for defense responses were induced to a lesser extent by the endophytes than by the pathogen, indicating a more compatible interaction.
Our results thus suggest that rice roots respond to endophytic colonization by inducing metabolic shifts and signaling events, for which the CSP is not essential.
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