Novel genes and alleles of the BTB/POZ protein family in Oryza rufipogon.

The BTB/POZ family of proteins is widespread in plants and animals, playing important roles in development, growth, metabolism, and environmental responses. Although members of the expanded BTB/POZ gene family (OsBTB) have been identified in cultivated rice (Oryza sativa), their conservation, novelty, and potential applications for allele mining in O. rufipogon, the direct progenitor of O. sativa ssp. japonica and potential wide-introgression donor, are yet to be explored. This study describes an analysis of 110 BTB/POZ encoding gene loci (OrBTB) across the genome of O. rufipogon as outcomes of tandem duplication events. Phylogenetic grouping of duplicated OrBTB genes was supported by the analysis of gene sequences and protein domain architecture, shedding some light on their evolution and functional divergence. The O. rufipogon genome encodes nine novel BTB/POZ genes with orthologs in its distant cousins in the family Poaceae (Sorghum bicolor, Brachypodium distachyon), but such orthologs appeared to have been lost in its domesticated descendant, O. sativa ssp. japonica. Comparative sequence analysis and structure comparisons of novel OrBTB genes revealed that diverged upstream regulatory sequences and regulon restructuring are the key features of the evolution of this large gene family. Novel genes from the wild progenitor serve as a reservoir of potential new alleles that can bring novel functions to cultivars when introgressed by wide hybridization. This study establishes a foundation for hypothesis-driven functional genomic studies and their applications for widening the genetic base of rice cultivars through the introgression of novel genes or alleles from the exotic gene pool.

The SlNAC2 transcription factor from tomato confers tolerance to drought stress in transgenic tobacco plants.

Drought is a key environmental factor that restricts crop growth and productivity. Plant responses to water-deficit stress at the whole plant level are mediated by stress-response gene expression through the action of transcription factors (TF). The NAC (NAM/ATAF/CUC) transcription factor family has been well documented in its role in improving plant abiotic stress tolerance. In the present study we evaluated the effects of overexpression of SlNAC2 TF on the photosynthetic machinery, relative water content (RWC), reactive oxygen species, antioxidants and proline levels in tobacco plants exposed to a water-deficit treatment. Shoot growth and seed formation were also evaluated before, during and following water-deficit to determine any morphological consequences of transgene expression. The transgenic plants maintained higher RWC and chlorophyll levels over 21 days after withholding water and stomatal conductance until the 16th day of water-deficit. Overexpression of SlNAC2 in tobacco increased proline levels, improved seed setting and delayed leaf senescence of the transgenic plants. Reactive oxygen species accumulated at lower levels in the dehydrated transgenic plants but no significant difference in superoxide dismutase and catalase content were seen between the genotypes. The conversion of glutathione to oxidized glutathione was significantly higher in the transgenic plants, supported by increased glutathione reductase transcript levels. Our results indicate that overexpression of SlNAC2 in tobacco improved survival during and recovery from water-deficit stress, without an associated biomass penalty under irrigation. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s12298-021-00996-2.