Genome-Wide Analysis of the Late Embryogenesis Abundant (LEA) and Abscisic Acid-, Stress-, and Ripening-Induced (ASR) Gene Superfamily from Canavalia rosea and Their Roles in Salinity/Alkaline and Drought Tolerance

Canavalia rosea (bay bean), distributing in coastal areas or islands in tropical and subtropical regions, is an extremophile halophyte with good adaptability to seawater and drought. Late embryogenesis abundant (LEA) proteins typically accumulate in response to various abiotic stresses, including dehydration, salinity, high temperature, and cold, or during the late stage of seed development. Abscisic acid-, stress-, and ripening-induced (ASR) genes are stress and developmentally regulated plant-specific genes. In this study, we reported the first comprehensive survey of the LEA and ASR gene superfamily in C. rosea. A total of 84 CrLEAs and three CrASRs were identified in C. rosea and classified into nine groups. All CrLEAs and CrASRs harbored the conserved motif for their family proteins. Our results revealed that the CrLEA genes were widely distributed in different chromosomes, and all of the CrLEA/CrASR genes showed wide expression features in different tissues in C. rosea plants. Additionally, we introduced 10 genes from different groups into yeast to assess the functions of the CrLEAs/CrASRs. These results contribute to our understanding of LEA/ASR genes from halophytes and provide robust candidate genes for functional investigations in plant species adapted to extreme environments.

Enrichment of Intrinsically Disordered Residues in Ohnologs Facilitate Abiotic Stress Resilience in Brassica Rapa

Background: Arabidopsis thaliana and Brassica rapa shared a common evolutionary clade but Brassica species experienced an extra whole genome triplication (WGT) event compared with the model plant A. thaliana. This extra round of WGT confers B. rapa more abiotic stress resistant. The study aims to unravel how the consequences of whole genome duplication steer the variation in stress adaptation competency between the two species.Result: Comparing the duplication status between abiotic stress resistant (ASR) genes in the two species, significant increase in the number of paralogs in ASR genes of B. rapa than A. thaliana was found. Investigation on the proteomic features suggests that the ohnologs pairs in both species are more enriched with intrinsically disordered residues (IDRs) than other duplicated pairs but IDRs only in B. rapa have showed a significant positive correlation with functional divergence between the duplicated pairs. The functional divergence helps to mediate more stress adaptation functions in the ohnologs of B. rapa than that of A. thaliana. Moreover, domain ontology analysis has revealed that the new domains with stress functions are significantly more enriched in the ohnologs of B. rapa. Interestingly, majority of these stress tolerant domains are found to be present in the intrinsically disordered regions of the proteins. Statistical analysis along with these observations make it reasonable to speculate that IDRs expedite stress adaption potentiality in B. rapa by enriching more stress related functions and accommodating stress specific domains in ohnologs of this plant species.Conclusion: With the occurrence of WGT in the Brassica species the stress resilience features of B. rapa as compared to A. thaliana is less studied. This study unveils the role of intrinsically disordered residues (IDRs) of ohnologs in optimizing more stress resilience in B. rapa than A. thaliana. Thus, it will open new avenues in understanding the mechanism of succeeding stress adaptation potentiality in B. rapa over evolutionary time.

Genome-wide identification and expression analysis of the apple ASR gene family in response to Alternaria alternata f. sp. mali

The ABA/water stress/ripening-induced (ASR) gene family exists universally in higher plants, and many ASR genes are up-regulated during periods of environmental stress and fruit ripening. Although a considerable amount of research has been performed investigating ASR gene response to abiotic stresses, relatively little is known about their roles in response to biotic stresses. In this report, we identified five ASR genes in apple (Malus × domestica) and explored their phylogenetic relationship, duplication events, and selective pressure. Five apple ASR genes (Md-ASR) were divided into two clades based on phylogenetic analysis. Species-specific duplication was detected in M. domestica ASR genes. Leaves of ‘Golden delicious’ and ‘Starking’ were infected with Alternaria alternata f. sp. mali, which causes apple blotch disease, and examined for the expression of the ASR genes in lesion areas during the first 72 h after inoculation. Md-ASR genes showed different expression patterns at different sampling times in ‘Golden delicious’ and ‘Starking’. The activities of stress-related enzymes, peroxidase (POD), superoxide dismutase (SOD), catalase (CAT), phenylalanine ammonia lyase (PAL), and polyphenoloxidase (PPO), and the content of malondialdehyde (MDA) were also measured in different stages of disease development in two cultivars. The ASR gene expression patterns and theses physiological indexes for disease resistance suggested that Md-ASR genes are involved in biotic stress responses in apple.