Yusta, R. | bioRxiv Science

bioRxiv2024

Photosynthetic and Genetic Adaptations Underpinning the Resilience of Cistanthe longiscapa in the Atacama Desert

O_LIThe Atacama Desert is one of the most hostile environments for life. However, the plant species Cistanthe longiscapa (C. longiscapa) completes its life cycle in the Atacama Desert after sporadic rainfall. C_LIO_LIPhysiological analyses under controlled environmental conditions revealed superior photosynthetic performance, better light acclimation mechanisms, and larger accumulation of photosystem II in C. longiscapa compared to its mesophilic sister species. C_LIO_LIC. longiscapa shows evolutionary expansions in gene families related to DNA repair, photosynthesis, and protein homeostasis. In addition, we observed substantial gene duplication and polymorphic variations between coastal and inland populations in the Atacama Desert. Finally, our assembled mitochondrial genome provides genetic information for all DNA-containing compartments of C. longiscapa. C_LIO_LIDiurnal oscillations of malic acid and time-resolved transcriptome analyses of plants harvested in the Atacama Desert indicate that C. longiscapa engages in CAM metabolism. We observed significant differences in transcripts encoding plastid-localized proteins, including those involved in carbon metabolism, light harvesting, and photoprotection, highlighting the critical role of chloroplasts in the adaptation of C. longiscapa to the Atacama Desert. C_LIO_LIOur study provides physiological and genetic evidence for the adaptations of C. longiscapa and advances our understanding of how plants can cope with extreme environmental conditions. C_LI

plant biology↗

bioRxiv2022

Transcriptomic reprogramming in a susceptible Phaseolus vulgaris L. variety during Pseudomonas syringae attack: The key role of homogalacturonan methylation

The susceptibility of common bean varieties to Pseudomonas syringae pv. phaseolicola (Pph) has been well-documented. However, the molecular mechanism that drives this susceptibility has not been clarified yet. In an attempt to understand this process, 15-day-old common bean plants, variety rinon, were infected with Pph to analyze the transcriptomic changes during the first steps of the infection (at 2 and 9 h). RNA-seq analysis showed an upregulation of defense-and signaling-related genes at 2h, most of them being downregulated at 9h, suggesting that Pph would inhibit the transcriptomic reprogramming of the plant. This trend was also observed in the modulation of 101 cell wall (CW) related genes, suggesting that Pph could produce/induce changes in the CW. However, the changes in CW composition at early stages of Pph infection were related to homogalacturonan (HG) methylation and the formation of HG egg boxes. From all HG-related genes modulated by the infection, a common bean pectin methylesterase inhibitor 3 (PvPMEI3) gene - closely related to AtPMEI3 -- was detected. In addition, PMEI3 protein was located in the apoplast and its PME inhibitory activity was demonstrated. Therefore, PvPMEI3 seems to be a good candidate to play a key role in Pph infection. This premise was supported by the analysis of Arabidopsis pmei3 mutant, which showed susceptibility to Pph, in contrast to resistant Col-0 control plants. All these changes could be an attempt to reinforce the CW structure and thus, hinder the attack of the bacterium. However, these transcriptional and CW-remodeling processes are neither maintained during the necessary time, nor are deep enough to block the action of the pathogen, facilitating the well-known susceptibility of rinon variety to Pph.

plant biology↗