The study reveals the mechanism by which desert cyanobacteria tolerate extreme dry dehydration

Recently, the internationally renowned academic journal PNAS published the latest research progress of Professor Qiu Baosheng’s research group of the School of Life Sciences of Central China Normal University on the drought resistance and dehydration of desert cyanobacteria, entitled “Coevolution of tandemly repeated hlips and RpaB-like transcriptional factor confers desiccation tolerance to.” subaerial Nostoc species”。

Desiccation is one of nature’s harshest stresses of adversity, which seriously affects the cellular structure and physiological function of living organisms. Although the vast majority of organisms cannot survive after dry dehydration, a few species can revive from a long-term state of complete dehydration, and this strange phenomenon of “dry but not dead” has always been a topic of interest to the biological community. In 1702, the father of the microscope, Anthony Leeuwenhoek, observed that rotifers could be resurrected after drying and dehydration, and scientists have since conducted extensive research on the drying dehydration tolerance of resuscitation organisms such as Saccharomyces cerevisiae, resuscitation plants, and tardigrades. In the past 20 years, the combined use of multi-omics techniques has provided some clues to the mechanism of biological tolerance to dry dehydration, in which several stress effector proteins are considered to play an important role. Since resuscitation organisms often lack a genetic operating system, the mechanism of action of these proteins in organisms, especially in photosynthetic organisms, remains unclear. Desert cyanobacteria play a key role in the formation of biological soil crusts and community succession, and revealing their unique photosynthetic protection mechanism in the process of drying and dehydration will help to better understand the dehydration tolerance strategy of photosynthetic organisms, and provide new ideas for technological innovation in ecological restoration of desertified land and drought-resistant breeding of crops.

Qiu Baosheng’s research group has been committed to the research of desert cyanobacteria for more than 20 years, and was invited to provide the State Forestry and Grassland Administration with the grading advice on the national first-level protection of wild plant hairweeds, which was adopted by the new edition of the “List of Wild Plants under National Key Protection” approved by the State Council. The research group took the lead in announcing and sharing the whole genome information of Facai to international counterparts, built a platform for transcriptional regulation network screening system of Facai, and used gene editing technology to break through the bottleneck of genetic operation technology of Facai, and then developed Facai into a model material for studying cyanobacteria in the desert.

On this basis, the research group identified a high-light-induced protein four-gene tandem repeat (hlip-cluster) in the hair vegetable genome, which plays an important role in the process of tolerating drying and dehydration of hair vegetables. This gene tandem repeat can specifically and rapidly respond to dry dehydration and upregulate expression. After the knockout mutants were obtained by gene editing technology, the repair ability of Optics II was impaired, and the ability to tolerate drying and dehydration decreased significantly. At the same time, hlip-cluster heterologous expression can significantly enhance the dehydration tolerance of the dehydration-sensitive algae plant Nostoc PCC 7120. Through the screening of transcription factor libraries, it was found that the transcription factor Hrf1 can synergistically regulate the expression of hlips-cluster and dry-induced psbA, which plays a negative regulatory role in the adaptation of hair vegetables to harsh desert habitats. Phylogenetic analysis showed that Hlip-cluster co-evolution with the transcription factor Hrf1 in terrestrial candida algae populations, which provided a new evolutionary perspective on the drought tolerance mechanisms of photosynthetic organisms.

The research group studies show that the Hrf1-hlips module in Candida can promote the rapid and efficient expression of hlips in the process of drying and dehydration, minimize the photodamage during the drying and dehydration process, so that it can quickly restore photosynthetic activity during the short rehydration growth window in the early morning, strive for more growth time, and survive in an extremely harsh desert environment.

Figure 1. The coevolution of the halip gene cluster and the transcription factor Hrf1 has allowed Candida terrestrial to gain resistance to drying and dehydration

The work was supported by the National Natural Science Foundation of China. Xu Haifeng, a postdoctoral fellow in the research group, was the first author of the paper, Associate Professor Dai Guozheng was the co-first author, doctoral students Bai Yang, postdoctoral student Shang Jinlong and others participated in the study, and Professor Shi Huazhong of Texas Technological University and Professor Aaron Kaplan of Hebrew University in Israel also made important contributions to the work. Professor Qiu Baosheng is the corresponding author of the paper, and Central China Normal University is the first unit to complete the paper.

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