Comparative transcriptome provides new insights into the molecular regulation of olive trees to chilling stress.

Olive (Olea europaea L.), an economically important oil-producing crop, is sensitive to low temperature, which severely limits its productivity and geographical distribution. However, the underlying mechanism of cold tolerance in olive remains elusive. In this study, a chilling experiment (4 °C) on the living saplings of two olive cultivars revealed that O. europaea cv. Arbequina showed stronger cold tolerance with greater photosynthetic activity compared with O. europaea cv. Leccino. Transcriptome analyses revealed that early light-inducible protein 1 (ELIP1), the main regulator for chlorophyll synthesis, is dramatically induced to protect the photosynthesis at low temperatures. Furthermore, weighted gene co-expression network analysis, yeast one-hybrid and luciferase assays demonstrated that transcription factor bHLH66 serves as an important regulator of ELIP1 transcription by binding to the G-box motif in the promoter. Taken together, our research revealed a novel transcriptional module consisting of bHLH66-ELIP1 in the adaptation of olive trees to cold stress.

The gapless genome assembly and multi-omics analyses unveil a pivotal regulatory mechanism of oil biosynthesis in the olive tree.

Olive is a valuable oil-bearing tree with fruits containing high levels of fatty acids. Oil production is a multifaceted process involving intricate interactions between fatty acid biosynthesis and other metabolic pathways that are affected by genetics and the developmental stages of the fruit. However, a comprehensive understanding of the underlying regulatory mechanisms is still lacking. Here, we generated a gap-free telomere-to-telomere assembly for Olea europaea cv. 'Leccino', representing an olive genome with the highest contiguity and completeness to date. The combination of time-course metabolomics and transcriptomics datasets revealed a negative correlation between fatty acid and flavonoid biosynthesis in the initial phase of olive fruit development, which was subject to an opposing regulatory mechanism mediated by the hub transcription factor MYC2. Multifaceted molecular assays demonstrated that MYC2 is a repressor of fatty acid biosynthesis by downregulating the expression of BCCP2 (biotin carboxylase carrier protein 2), while it acts as an activator of FLS (flavonol synthase), leading to an increase in flavonoid synthesis. Furthermore, the expression of MYC2 is regulated by fluctuations of methyl jasmonate content during olive fruit development. Our study completes a high-quality gapless genome of an olive cultivar, and provides new insight into the regulatory mechanisms underlying the biosynthesis of fatty acids and flavonoids in its fruit.

Investigation of the effect of fly ash content on the bonding performance of CFRP-concrete interface in sulfate environment.

The present study focuses on the investigation of the interfacial bond behavior of carbon fiber-reinforced polymer (CFRP)-concrete under dry-wet sulfate cycles by double-sided shear testing. Besides, the effects of fly ash content on the interfacial failure characteristics, interfacial debonding bearing capacity, CFRP strain distribution, and interfacial shear stress peak were analyzed. The interfacial debonding capacity, maximum CFRP strain, and peak value of interfacial shear stress of the CFRP-concrete interface decreased with increasing erosion time under the sulfate dry-wet cycle's action, according to the sulfate dry-wet cycle test results. The sulfate resistance of the CFRP-concrete interface increased after the addition of fly ash. However, the final decrease amplitude of interfacial debonding capacity, CFRP maximum strain, and maximum interfacial shear stress all reduced as the fly ash content increased. The effective bond length of the interface gradually increased with increasing erosion time; however, the change in fly ash content had little effect on the effective bond length, and the final effective bond length of the samples with different fly ash content was the same. Moreover, the CFRP-concrete interfacial bearing capacity model under the sulfate dry-wet cycle was established by introducing sulfate's comprehensive influence coefficient and considering fly ash content's influence. In conclusion, the comparative analysis of the prediction model and test results revealed that the prediction model could well reflect the degradation law of interfacial debonding bearing capacity with sulfate attack time.