Genome-wide identification and analysis of the sucrose synthase gene family in cassava (Manihot esculenta Crantz).

Sucrose synthase (SUS), a key enzyme of the sucrose metabolism pathway, is encoded by a multi-gene family in plants. To date, dozens of SUS gene families have been characterized in various plant genomes. However, only a few studies have performed comprehensive analyses in tropical crops like cassava (Manihot esculenta Crantz). In the present study, seven non-redundant members of the SUS gene family (MeSUS1-7) were identified and characterized from the cassava genome. The MeSUS genes were distributed on five chromosomes (Chr1, Chr2, Chr3, Chr14, and Chr16) and the encoded proteins could be classified into three major groups with other SUS proteins from both dicot and monocot species (SUS I, SUS II, and SUS III). The spatio-temporal expression profiles of MeSUS genes showed a developmental stage-dependent, partially overlapping pattern, mainly expressed in the source and sink tissues. Cold and drought treatments significantly induced the expressions of MeSUS2, MeSUS4, MeSUS6, and MeSUS7 and the activities of the encoded enzymes, indicating that these genes may play crucial roles in resistance against abiotic stresses. These results provide new insights into the multifaceted role of the SUS gene family members in various physiological processes, especially sucrose transport and starch accumulation in cassava roots.

Molecular cloning and expression analysis of sucrose phosphate synthase genes in cassava (Manihot esculenta Crantz).

Sucrose phosphate synthase (SPS), a key rate-limiting enzyme in the sucrose biosynthesis pathway in plants, is encoded by a multi-gene family. Until recently, the identification and characterization of the SPS gene family have been performed for dozens of plant species; however, few studies have involved a comprehensive analysis of the SPS family members in tropical crops, such as cassava (Manihot esculenta Crantz). In the current study, five SPS genes (MeSPS1, MeSPS2, MeSPS3, MeSPS4, and MeSPS5) were isolated from cassava, and their sequence characteristics were comprehensively characterized. These MeSPS genes were found distributed on five chromosomes (Chr2, Chr14, Chr15, Chr16, and Chr18). Phylogenetic analysis showed that the MeSPS protein sequences were clustered into three families, together with other SPS sequences from both dicot and monocot species (families A, B, and C). The spatio-temporal expression pattern analysis of MeSPS genes showed a tissue-specific and partially overlapping expression pattern, with the genes mainly expressed in source tissues during cassava growth and development. Correlation analysis revealed that the expression of MeSPS genes correlated positively with root starch content, indicating that the expression of MeSPS genes might accelerate the rate of starch accumulation in the roots of cassava plants.

Analysis of leaf morphology, secondary metabolites and proteins related to the resistance to Tetranychus cinnabarinus in cassava (Manihot esculenta Crantz).

Constitutive resistance of plant can be divided into physical and chemical barriers. Cassava (Manihot esculenta Crantz) is susceptible to mites, especially Tetranychus cinnabarinus. Although significant differences in the resistance to T. cinnabarinus are observed in different cassava cultivars, limited research has been done on the mechanism accounting for the resistance. The aim of this study was to explore the mechanism of resistance to T. cinnabarinus by comparing morphology, secondary metabolites and proteins in different cassava cultivars. The anatomical structure of leaves showed that the cassava cultivar Xinxuan 048 (XX048), which showed a stronger resistance to T. cinnabarinus in both greenhouse testing and three years field evaluation tests (2016-2018), had thicker palisade tissue, spongy tissue, lower epidermis and leaf midrib tissue compared to cultivar Guire 4 (GR4). Greenhouse evaluation demonstrated that originally these cultivars were different, leading to differences in constitutive levels of metabolites. The proteomic analysis of protected leaves in XX048 and GR4 revealed that up-regulated differentially expressed proteins (DEPs) were highly enriched in secondary metabolic pathways, especially in the biosynthesis of flavonoids. This study not only provides a comprehensive data set for overall proteomic changes of leaves in resistant and susceptible cassava, but also sheds light on the morphological characteristics of cassava-mite interaction, secondary metabolite defense responses, and molecular breeding of mite-resistant cassava for effective pest control.

Genome-wide identification and expression of GRAS gene family members in cassava.

BACKGROUND: Cassava is highly tolerant to stressful conditions, especially drought stress conditions; however, the mechanisms underlying this tolerance are poorly understood. The GRAS gene family is a large family of transcription factors that are involved in regulating the growth, development, and stress responses of plants. Currently, GRAS transcription factors have not been systematically studied in cassava, which is the sixth most important crop in the world. RESULTS: Seventy-seven MeGRAS genes were identified from the cassava genome database. Phylogenetic analysis revealed that the MeGRAS proteins could be divided into 14 subfamilies. The gene structure and motif compositions of the proteins were considerably conserved within the same subfamily. Duplication events, particularly segmental duplication, were identified as the main driving force for GRAS gene expansion in cassava. Global expression analysis revealed that MeGRAS genes exhibited similar or distinct expression profiles within different tissues among different varieties. Moreover, qRT-PCR analysis revealed the expression patterns of MeGRAS genes in response to abiotic stress (drought, salt, cold, and H2O2), and the results suggest that these genes may have multiple functions. CONCLUSION: This study is the first to provide comprehensive information on GRAS gene family members in cassava. The data will increase our understanding of both the molecular basis and the effects of GRAS genes. In addition, the results will contribute further to identifying the responses to various environmental conditions and provide insights into the potential functions of GRAS genes.