Genetic and Molecular Characterization of Submergence Response Identifies Subtol6 as a Major Submergence Tolerance Locus in Maize

Abstract

Maize is highly sensitive to short term flooding and submergence. Early season flooding reduces germination, survival and growth rate of maize seedlings. We aimed to discover genetic variation for submergence tolerance in maize and elucidate the genetic basis of submergence tolerance through transcriptional profiling and linkage analysis of contrasting genotypes. A diverse set of maize nested association mapping (NAM) founder lines were screened, and two highly tolerant (Mo18W and M162W) and sensitive (B97 and B73) genotypes were identified. Tolerant lines exhibited delayed senescence and lower oxidative stress levels compared to sensitive lines. Transcriptome analysis was performed on these inbreds to provide genome level insights into the molecular responses to submergence. Tolerant lines had higher transcript abundance of several fermentation-related genes and an unannotated Pyrophosphate-Dependent Fructose-6-Phosphate 1-Phosphotransferase gene during submergence. A coexpression network enriched for CBF (C-REPEAT/DRE BINDING FACTOR: C-REPEAT/DRE BINDING FACTOR) genes, was induced by submergence in all four inbreds, but was more activated in the tolerant Mo18W. A recombinant inbred line (RIL) population derived from Mo18W and B73 was screened for submergence tolerance. A major QTL named Subtol6 was mapped to chromosome 6 that explains 22% of the phenotypic variation within the RIL population. We identified two candidate genes (HEMOGLOBIN2 and RAV1) underlying Subtol6 based on contrasting expression patterns observed in B73 and Mo18W. Sources of tolerance identified in this study (Subtol6) can be useful to increase survival rate during flooding events that are predicted to increase in frequency with climate change.

Transcriptomic analysis of submergence-tolerant and sensitive Brachypodium distachyon ecotypes reveals oxidative stress as a major tolerance factor

“…3d). Interestingly, Campbell et al 28. also found a constitutively expressed HB1 concomitant with the down-regulation of AOX in maize varieties with superior submergence tolerance, opening the possibility that this mechanism may be extended to agriculturally relevant grasses.…”

“…; Panicoideae ) and rice ( Oryza sativa ; Ehrhartoideae ), provide ≈50% of human caloric intake, with this proportion being even higher in developing countries25. However, molecular characterization of the mechanisms for tolerance to submergence in the grasses is uneven: in rice, this endeavour has been sustained for decades26, it has recently started in barley ( Hordeum vulgare )27 and maize28 and only physiological characterization has been defined in wheat and sugarcane2930. The natural genetic diversity of rice and maize has been used to find molecular mechanisms that are differentially expressed in tolerant versus sensitive varieties2831.…”

Transcriptomic diversity in seedling roots of European flint maize in response to cold

“…The substantial transcriptomic variation between genotypes in this study provided the opportunity to evaluate the response to cold stress in a genetically diverse germplasm. In contrast, previous transcriptome studies on abiotic stress tolerance such as waterlogging, cold stress, drought stress typically focused on only one or a few maize inbred lines or hybrids under different conditions [15,[34][35][36][37][38][39][40].…”

Group VII Ethylene Response Factors in Arabidopsis: Regulation and Physiological Roles

“…Thus, the same protective mechanisms can act as an integral part of the ERF-VII dependent response strategy to hypoxia. Improved ROS management has been associated with superior submergence tolerance in maize and Brachypodion distachyon (Campbell et al, 2015;Rivera-Contreras et al, 2016), while the activation of antioxidant responses in the posthypoxic phase is crucial for survival in Arabidopsis (Paradiso et al, 2016;Yuan et al, 2017). Interestingly, a target of RAP-type ERF-VIIs, namely HYPOXIA RE-SPONSIVE UNIVERSAL STRESS PROTEIN1, has been shown to coordinate oxygen sensing by PCO/RAP2.12 with H 2 O 2 production by NADPH oxidases, indicating that there is a network connecting diverse signaling pathways downstream of ERF-VII targets (Gonzali et al, 2015).…”