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Contributions of Adaptive Plant Architecture to Transgressive Salinity Tolerance in Recombinant Inbred Lines of Rice: Molecular Mechanisms Based on Transcriptional Networks

Genetic novelties are important nucleators of adaptive speciation.‎ Transgressive segregation is a major mechanism that creates genetic novelties with morphological and developmental attributes that confer adaptive advantages in certain environments.‎ This study examined the morpho-developmental and physiological profiles of recombinant inbred lines (RILs) from the salt-sensitive IR29 and salt-tolerant Pokkali rice, representing the total range of salt tolerance including the outliers at both ends of the spectrum.‎

Morpho-developmental and physiological profiles were integrated with a hypothesis driven interrogation of mRNA and miRNA transcriptomes to uncover the critical genetic networks that have been rewired for novel adaptive architecture.‎ The transgressive super-tolerant FL510 had a characteristic small tiller angle and wider, more erect, sturdier, and darker green leaves.‎ This unique morphology resulted in lower transpiration rate, which also conferred a special ability to retain water more efficiently for osmotic avoidance.‎ The unique ability for water retention conferred by such adaptive morphology appeared to enhance the efficacy of defenses mediated by NaC exclusion mechanism (SalTol-effects) inherited from Pokkali.‎ The super-tolerant FL510 and super-sensitive FL499 had the smallest proportions of differentially expressed genes with little overlaps.‎

Genes that were steadily upregulated in FL510 comprised a putative cytokinin regulated genetic network that appeared to maintain robust growth under salt stress through well-orchestrated cell wall biogenesis and cell expansion, likely through major regulatory (OsRR23, OsHK5) and biosynthetic (OsIPT9) genes in the cytokinin signaling pathway.‎ Meanwhile, a constitutively expressed cluster in FL510 prominently featured two transcription factors (OsIBH1, TAC3) that control tiller angle and growth habit through the brassinosteroid signaling pathway.‎ Both the putative cytokinin-mediated and brassinosteroid-mediated clusters appeared to function as highly coordinated network synergies in FL510.‎ In contrast, both networks appeared to be sub-optimal and inferior in the other RILs and parents as they were disjointed and highly fragmented.‎ Transgressively expressed miRNAs (miR169, miR397, miR827) were also identified as prominent signatures of FL510, with functional implications to mechanisms that support robust growth, homeostasis, and osmotic stress avoidance.‎ Results of this study demonstrate how genetic recombination creates novel morphology that complements inducible defenses hence transgressive adaptive phenotypes.‎

Authors: 
Isaiah Catalino M.‎ Pabuayon, Ai Kitazumi, Glenn B.‎ Gregorio, Rakesh Kumar Singh, Benildo G.‎ de los Reyes
Year: 
۲۰۲۰
Publication type: 
Scientific Paper
Publication Source: 
Frontiers in Genetics
Volume/Chapter/Issue: 
۱۱