title: Functional mechanisms of drought tolerance in subtropical maize (Zea mays L.) identified using genome-wide association mapping.
abstract: BACKGROUND
  Earlier studies were focused on the genetics of temperate and tropical maize under drought. We identified genetic loci and their association with functional mechanisms in 240 accessions of subtropical maize using a high-density marker set under water stress.
  
  
  RESULTS
  Out of 61 significant SNPs (11 were false-discovery-rate-corrected associations), identified across agronomic traits, models, and locations by subjecting the accessions to water stress at flowering stage, 48% were associated with drought-tolerant genes. Maize gene models revealed that SNPs mapped for agronomic traits were in fact associated with number of functional traits as follows: stomatal closure, 28; flowering, 15; root development, 5; detoxification, 4; and reduced water potential, 2. Interactions of these SNPS through the functional traits could lead to drought tolerance. The SNPs associated with ABA-dependent signalling pathways played a major role in the plant's response to stress by regulating a series of functions including flowering, root development, auxin metabolism, guard cell functions, and scavenging reactive oxygen species (ROS). ABA signalling genes regulate flowering through epigenetic changes in stress-responsive genes. ROS generated by ABA signalling are reduced by the interplay between ethylene, ABA, and detoxification signalling transductions. Integration of ABA-signalling genes with auxin-inducible genes regulates root development which in turn, maintains the water balance by regulating electrochemical gradient in plant.
  
  
  CONCLUSIONS
  Several genes are directly or indirectly involved in the functioning of agronomic traits related to water stress. Genes involved in these crucial biological functions interacted significantly in order to maintain the primary as well as exclusive functions related to coping with water stress. SNPs associated with drought-tolerant genes involved in strategic biological functions will be useful to understand the mechanisms of drought tolerance in subtropical maize.
authors.affiliation: Division of Genetics, Indian Agricultural Research Institute, Pusa, New Delhi 110012, India. tnepolean@gmail.com.
authors.forename: Nepolean
authors.initials: N
authors.lastname: Thirunavukkarasu
authors.forename: Firoz
authors.initials: F
authors.lastname: Hossain
authors.forename: Kanika
authors.initials: K
authors.lastname: Arora
authors.forename: Rinku
authors.initials: R
authors.lastname: Sharma
authors.forename: Kaliyugam
authors.initials: K
authors.lastname: Shiriga
authors.forename: Swati
authors.initials: S
authors.lastname: Mittal
authors.forename: Sweta
authors.initials: S
authors.lastname: Mohan
authors.forename: Pottekatt Mohanlal
authors.initials: PM
authors.lastname: Namratha
authors.forename: Sreelatha
authors.initials: S
authors.lastname: Dogga
authors.forename: Tikka Shobha
authors.initials: TS
authors.lastname: Rani
authors.forename: Sumalini
authors.initials: S
authors.lastname: Katragadda
authors.forename: Abhishek
authors.initials: A
authors.lastname: Rathore
authors.forename: Trushar
authors.initials: T
authors.lastname: Shah
authors.forename: Trilochan
authors.initials: T
authors.lastname: Mohapatra
authors.forename: Hari Shankar
authors.initials: HS
authors.lastname: Gupta
mesh_terms: D002874:Chromosome Mapping; D055864:Droughts; D044127:Epigenesis, Genetic / Q000235:genetics; D017343:Genes, Plant / Q000235:genetics; D055106:Genome-Wide Association Study; D010641:Phenotype; D020641:Polymorphism, Single Nucleotide; D015398:Signal Transduction / Q000235:genetics; D013312:Stress, Physiological / Q000235:genetics; D014329:Tropical Climate; D003313:Zea mays / Q000166:cytology / Q000235:genetics* / Q000378:metabolism / Q000502:physiology*