Abiotic stresses adversely affect cellular homeostasis, impairing overall growth and development of plants. These initial stress signals activate downstream signalling processes, which, subsequently, activate stress-responsive mechanisms to re-establish homeostasis. Dehydrins (DHNs) play an important role in combating dehydration stress. Rice (Oryza sativa L.), which is a paddy crop, is susceptible to drought stress. As drought survival in rice might be viewed as a trait with strong evolutionary selection pressure, we observed DHNs in the light of domestication during the course of evolution. Overall, 65 DHNs were identified by a genome-wide survey of 11 rice species, and 3 DHNs were found to be highly conserved. The correlation of a conserved pattern of DHNs with domestication and diversification of wild to cultivated rice was validated by synonymous substitution rates, indicating that Oryza rufipogon and Oryza sativa ssp. japonica follow an adaptive evolutionary pattern; whereas Oryza nivara and Oryza sativa ssp. indica demonstrate a conserved evolutionary pattern. A comprehensive analysis of tissue-specific expression of DHN genes in japonica and their expression profiles in normal and PEG (poly ethylene glycol)-induced dehydration stress exhibited a spatiotemporal expression pattern. Their interaction network reflects the cross-talk between gene expression and the physiological processes mediating adaptation to dehydration stress. The results obtained strongly indicated the importance of DHNs, as they are conserved during the course of domestication.

AP2/ERF domain containing transcription factor super family is one of the important regulators in the plant kingdom. The involvement of AP2/ERF family members has been elucidated in various processes associated with plant growth, development as well as in response to hormones, biotic and abiotic stresses. In this study, we carried out genome-wide analysis to identify members of AP2/ERF family in Musa acuminata (A genome) and Musa balbisiana (B genome) and changes leading to neofunctionalisation of genes. Analysis identified 265 and 318 AP2/ERF encoding genes in M. acuminata and M. balbisiana respectively which were further classified into ERF, DREB, AP2, RAV and Soloist groups. Comparative analysis indicated that AP2/ERF family has undergone duplication, loss and divergence during evolution and speciation of the Musa A and B genomes. We identified nine genes which are up-regulated during fruit ripening and might be components of the regulatory machinery operating during ethylene-dependent ripening in banana. Tissue-specific expression analysis of the genes suggests that different regulatory mechanisms might be involved in peel and pulp ripening process through recruiting specific ERFs in these tissues. Analysis also suggests that MaRAV-6 and MaERF026 have structurally diverged from their M. balbisiana counterparts and have attained new functions during ripening.

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