Abscisic-acid-responsive StlncRNA13558 induces StPRL expression to increase potato resistance to Phytophthora infestans infection.

Late blight, caused by Phytophthora infestans, is one of the most serious diseases affecting potatoes (Solanum tuberosum L.). Long non-coding RNAs (lncRNAs) are transcripts with a length of more than 200 nucleotides that have no protein-coding potential. Few studies have been conducted on lncRNAs related to plant immune regulation in plants, and the molecular mechanisms involved in this regulation require further investigation. We identified and screened an lncRNA that specifically responds to P. infestans infection, namely, StlncRNA13558. P. infestans infection activates the abscisic acid (ABA) pathway, and ABA induces StlncRNA13558 to enhance potato resistance to P. infestans. StlncRNA13558 positively regulates the expression of its co-expressed PR-related gene StPRL. StPRL promotes the accumulation of reactive oxygen species and transmits a resistance response by affecting the salicylic acid hormone pathway, thereby enhancing potato resistance to P. infestans. In summary, we identified the potato late blight resistance lncRNA StlncRNA13558 and revealed its upstream and downstream regulatory relationship of StlncRNA13558. These results improve our understanding of plant-pathogen interactions' immune mechanism and elucidate the response mechanism of lncRNA-target genes regulating potato resistance to P. infestans infection.

Tomato chlorosis virus p22 interacts with NbBAG5 to inhibit autophagy and regulate virus infection.

Tomato chlorosis virus (ToCV) is a member of the genus Crinivirus in the family Closteroviridae. It has a wide host range and wide distribution, causing serious harm to the vegetable industry. The autophagy pathway plays an important role in plant resistance to virus infection. Viruses and plant hosts coevolve in defence and antidefence processes around autophagy. In this study, the interaction between ToCV p22 and Nicotiana benthamiana B-cell lymphoma2-associated athanogenes5 Nicotiana benthamiana (NbBAG5) was examined. Through overexpression and down-regulation of NbBAG5, results showed that NbBAG5 could negatively regulate ToCV infection. NbBAG5 was found to be localized in mitochondria and can change the original localization of ToCV p22, which is colocalized in mitochondria. NbBAG5 inhibited the expression of mitophagy-related genes and the number of autophagosomes, thereby regulating viral infection by affecting mitophagy. In summary, this study demonstrated that ToCV p22 affects autophagy by interacting with NbBAG5, established the association between viral infection, BAG proteins family, and the autophagy pathway, and explained the molecular mechanism by which ToCV p22 interacts with NbBAG5 to inhibit autophagy to regulate viral infection.

RAP2.6 enhanced salt stress tolerance by reducing Na+ accumulation and stabilizing the electron transport in Arabidopsis thaliana.

The transcription factors of the AP2/ERF family are involved in plant growth and development and responses to biotic and abiotic stresses. Here, we found RAP2.6, a transcription factor which belongs to the ERF subfamily, was responsive to salt stress in Arabidopsis. Under salt stress conditions, rap2.6 mutant seedlings were the sensitivity deficiency to salt stress which was reflected in higher germination rate and longer root length compared to the wild type. Also, the expressions of salt-related gene including SOS1, SOS2, SOS3, NHX1, NHX3, NHX5 and HKT1 in rap2.6 mutant seedlings were lower than the wild type under salt stress. rap2.6 mutant adult lacked salt stress tolerance based on the results of the phenotype, survival rates and ion leakage. Compared to wild type, rap2.6 mutant adult accumulated more Na+ in leaves and roots while the salt-related gene expressions were lower. In addition, the photosynthetic electron transport and PSII energy distribution in rap2.6 mutant plant leaves had been more seriously affected under salt stress conditions compared to the wild type. In summary, this study identified essential roles of RAP2.6 in regulating salt stress tolerance in Arabidopsis.

StICE1 enhances plant cold tolerance by directly upregulating StLTI6A expression.

KEY MESSAGE: Under cold conditions, StICE1 enhances plant cold tolerance by upregulating StLTI6A expression to maintain the cell membrane stability. Cold stress affects potato plants growth and development, crop productivity and quality. The ICE-CBF-COR regulatory cascade is the well-known pathway in response to cold stress in plants. ICE1, as a MYC-like bHLH transcription factor, can regulate the expressions of CBFs. However, whether ICE1 could regulate other genes still need to be explored. Our results showed that overexpressing ICE1 from potato in Arabidopsis thaliana could enhance plant cold tolerance. Under cold stress, overexpressed StICE1 in plants improved the stability of cell membrane, enhanced scavenging capacity of reactive oxygen species and increased expression levels of CBFs and COR genes. Furthermore, StICE1 could bind to the promoter of StLTI6A gene, which could maintain the stability of the cell membrane, to upregulate StLTI6A expression under cold conditions. Our findings revealed that StICE1 could directly regulate StLTI6A, CBF and COR genes expression to response to cold stress.

StLTO1, a lumen thiol oxidoreductase in Solanum tuberosum L., enhances the cold resistance of potato plants.

Cold stress reduces plant photosynthesis and increases the accumulation of reactive oxygen species (ROS) in plants, thereby dramatically affecting plant growth, crop productivity and quality. Here, we report that lumen thiol oxidoreductase 1 (StLTO1), a vitamin K epoxide reductase (VKOR)-like protein in the thylakoid membrane of Solanum tuberosum L., enhances the cold tolerance of potato plants. Under normal conditions, overexpression of StLTO1 in plants promoted plant growth. In addition, potato plants overexpressing StLTO1 displayed enhanced photosynthetic capacity and increased capacity for scavenging ROS compared to StLTO1 knockdown and wild-type potato plants under cold conditions. Overexpression of StLTO1 in potato plants also improved cold-regulated (COR) gene expression after cold stress. Our results suggest that StLTO1 acts as a positive regulator of cold resistance in potato plants.

StATL2-like could affect growth and cold tolerance of plant by interacting with StCBFs.

KEY MESSAGE: Our results confirmed that StATL2-like could interact with StCBFs and regulate plant growth. Meanwhile, StATL2-like acted as a negative regulator on low-temperature tolerance in plants. As important transcription factors for resisting many kinds of stresses, C-repeat-binding factors (CBF) play a key role in plant low-temperature tolerance by increasing COR genes expressions. Here, we report that StATL2-like, a RING-H2 E3 ubiquitin in Solanum tuberosum L., interacted with StCBF1 and StCBF4, respectively. AtATL2 is a highly homologous gene of StATL2-like in Arabidopsis thaliana. Under normal conditions, atl2 Arabidopsis mutant showed a growth inhibition phenotype while overexpressed StATL2-like in wild type Arabidopsis and atl2 mutant promoted plant growth. Besides, atl2 mutant had better low-temperature tolerance compared with wild type and StATL2-like transgenic lines which demonstrated that StATL2-like acted as a negatively regulator on low-temperature tolerance in plant. Moreover, atl2 mutant improved the scavenging capacity of reactive oxygen species (ROS) and alleviate the damage of photosynthetic system II (PSII) compared with StATL2-like transgenic lines under cold conditions. These results suggested a new component in CBF-dependent pathway to regulate plant growth and response to low-temperature stress in potato plants.

The network centered on ICEs play roles in plant cold tolerance, growth and development.

MAIN CONCLUSION: ICEs are key transcription factors in response to cold in plant, they also balance plant growth and stress tolerance. Thus, we systematize the information about ICEs published to date. Low temperature is an important factor affecting plant growth and development. Exposing to cold condition results in a suit of effects on plants including reduction of plant growth and reproduction, and decrease in crop yield and quality. Plants have evolved a series of strategies to deal with cold stress such as reprogramming of the expression of genes and transcription factors. ICEs (Inducer of CBF Expression), as transcription factors regulating CBFs (C-repeat binding factor), play key roles in balancing plant growth and stress tolerance. Studies on ICEs focused on the function of ICEs on cold tolerance, growth and development; post-translational modifications of ICEs and crosstalk between the ICEs and phytohormones. In this review, we focus on systematizing the information published to date. We summarized the main advances of the functions of ICEs on the cold tolerance, growth and development. And we also elaborated the regulation of ICEs protein stability including phosphorylation, ubiquitination and SUMOylation of ICE. Finally, we described the function of ICEs in the crosstalk among different phytohormone signaling pathway and cold stress. This review provides perspectives for ongoing research about cold tolerance, growth and development in plant.