Rice pyramided line IRBB67 (Xa4/Xa7) homeostasis under combined stress of high temperature and bacterial blight

Abstract

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 upregulated and down-regulated genes demonstrates how resistant plants cope with combined biotic and abiotic stresses. The world population is projected to reach 9.7 billion by 2050 and half the world population growth is expected in developing countries 1. This world population growth coupled with the impact of climate change on agricultural production in those countries demands a rapid growth in the food supply and animal feed, while conserving forest resources for climate mitigation 2,3. Previous reports have shown that an increase of seasonal temperature by 1 °C results in a decline of major grains yield in the range of 2.5 to 16% in the tropics and subtropics 4,5. Unfortunately, due to their sessile lifestyle, plants have no chance to escape this environment (biotic and abiotic stresses) and must respond and adapt 6-8. Abiotic stress may imply positive or negative effects on plant defense responses 7-9. According to these authors, the outcome of the interaction depends on the timing, nature and the severity of the stress. Temperature, water, relative humidity, light and circadian rhythm significantly influence plant defense and pathogen invasion 6. A small variation in temperature can affect plant growth, but also plants' responses to pests and pathogens 10,11. Most studies on plant responses to environmental changes were carried out under single stress and are therefore unsuccessful in explaining plant responses to more than one stress factor 9. High t...

Every cloud has a silver lining: how abiotic stresses affect gene expression in plant-pathogen interactions

“…Thirdly, genotype plays an important role in the way plants integrate multistress signals. For example, high temperatures decrease the resistance to X. oryzae of rice carrying Xa4 resistance but increase resistance of rice carrying Xa7 resistance , and this is correlated with genotype-specific transcriptomic profiles under the multistress combination ( Table 1 ; Dossa et al , 2020 ). The importance of genotype is supported by the involvement of PBS3 , an actor in SA signaling, in the age-dependent trade-off between two abiotic stresses and immune responses in Arabidopsis ( Berens et al , 2019 ): immune responses are reduced by drought and high salinity in older leaves, but not in younger leaves in which PBS3 antagonizes the trade-off.…”

Deployment of Genetic and Genomic Tools Toward Gaining a Better Understanding of Rice-Xanthomonasoryzae pv. oryzae Interactions for Development of Durable Bacterial Blight Resistant Rice

“…These contrasting scenarios raise concerns about durability of single R gene and different gene combinations in the scenario of a rapidly changing climate. Recently, Dossa et al (2020) demonstrated that near isogenic line IRBB 67 (owning BB resistance genes Xa4 and Xa7) did not show any difference in lesion length at both lower and higher temperature regimes, indicating that the reduced effectiveness of Xa4 at higher temperature did not affect the resistance level of IRBB 67.…”

The Heat is On: How Crops Respond to High Temperature

“…Insects propagate more at higher temperature and show increased feeding voracity across an increasing temperature range (Havko et al, 2020). In rice, high temperature contributes to bacterial blight development in field situations, and the disease severity is particularly high in the hot season (Dossa et al, 2020). For more examples related to high temperature-induced disease susceptibility we refer to a recent review (Cohen & Leach, 2020).…”

“…Bacterial blight caused by Xanthomonas oryzae pv. oryzae(Xoo ) leads to substantial yield loss in rice (Dossa et al, 2020). Xa7, one of the Resistance genes (R -genes) against pathogens (Zhang et al, 2015), effectively confers resistance to Xoo at high temperatures, but not at low temperature (Cohen et al, 2017;Dossa et al, 2020;Webb et al, 2010).…”

“…oryzae(Xoo ) leads to substantial yield loss in rice (Dossa et al, 2020). Xa7, one of the Resistance genes (R -genes) against pathogens (Zhang et al, 2015), effectively confers resistance to Xoo at high temperatures, but not at low temperature (Cohen et al, 2017;Dossa et al, 2020;Webb et al, 2010). The other way around, some biotic stresses mitigate the impairment caused by high temperature stress in crops (Anfoka et al, 2016;Mathur, Sharma, & Jajoo, 2018).…”