Abstract
Oryza officinalis is an accessible alien donor for genetic improvement of rice. Comparison across a representative panel of Oryza species showed that the wild O. officinalis and cultivated O. sativa ssp. japonica have similar cold tolerance potentials. The possibility that either distinct or similar genetic mechanisms are involved in the low temperature responses of each species was addressed by comparing their transcriptional networks. General similarities were supported by shared transcriptomic signatures indicative of equivalent metabolic, hormonal, and defense status. However, O. officinalis has maintained an elaborate cold-responsive brassinosteroid-regulated BES1-network that appeared to have been fragmented in O. sativa. BES1-network is potentially important for integrating growth-related responses with physiological adjustments and defenses through the protection of photosynthetic machinery and maintenance of stomatal aperture, oxidative defenses, and osmotic adjustment. Equivalent physiological processes are functional in O. sativa but their genetic mechanisms are under the direct control of ABA-dependent, DREB-dependent and/or oxidative-mediated networks uncoupled to BES1. While O. officinalis and O. sativa represent long periods of speciation and domestication, their comparable cold tolerance potentials involve equivalent physiological processes but distinct genetic networks. BES1-network represents a novel attribute of O. officinalis with potential applications in diversifying or complementing other mechanisms in the cultivated germplasm.
Highlights
The domesticated rice (Oryza sativa L.) represents only a fraction of the total genetic potential of the genus[1,2,3]
The relative ranking of accessions revealed by Standard Evaluation Score (SES) and electrolyte leakage index (ELI) was generally consistent with the proposed ranking in the bioclimatic model
A series of RNA-Seq libraries (DDBJDRA006704) was constructed to investigate whether distinct mechanisms are involved in the expression of similar cold tolerance potential in IRGC100896 and Nipponbare (Supplementary Table S2)
Summary
The domesticated rice (Oryza sativa L.) represents only a fraction of the total genetic potential of the genus[1,2,3]. Successful efforts for agronomic trait introgression from wild Oryza to cultivars involved either a diploid CC-genome (O. officinalis) or allotetraploid CC-combination (O. minuta, O. latifolia) as donors[13,14,15]. This shows that CC-genome is a more accessible alien donor for the diversification of the genetic base of cultivars[16]. While the Asian cultivated rice is generally very cold-sensitive, a number of temperate japonica cultivars have been used as donors of tolerance-associated traits[17,18]. The genetic mechanism revealed in this study is an important first step for understanding the finer details behind the hidden potentials of the Oryza CC-genome for diversifying the genetic mechanisms that exist in cultivars
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