Transcriptomic analysis of salt stress responsive genes in Rhazya stricta

Abstract

Rhazya stricta is an evergreen shrub that is widely distributed across Western and South Asia, and like many other members of the Apocynaceae produces monoterpene indole alkaloids that have anti-cancer properties. This species is adapted to very harsh desert conditions making it an excellent system for studying tolerance to high temperatures and salinity. RNA-Seq analysis was performed on R. stricta exposed to severe salt stress (500 mM NaCl) across four time intervals (0, 2, 12 and 24 h) to examine mechanisms of salt tolerance. A large number of transcripts including genes encoding tetrapyrroles and pentatricopeptide repeat (PPR) proteins were regulated only after 12 h of stress of seedlings grown in controlled greenhouse conditions. Mechanisms of salt tolerance in R. stricta may involve the upregulation of genes encoding chaperone protein Dnaj6, UDP-glucosyl transferase 85a2, protein transparent testa 12 and respiratory burst oxidase homolog protein b. Many of the highly-expressed genes act on protecting protein folding during salt stress and the production of flavonoids, key secondary metabolites in stress tolerance. Other regulated genes encode enzymes in the porphyrin and chlorophyll metabolic pathway with important roles during plant growth, photosynthesis, hormone signaling and abiotic responses. Heme biosynthesis in R. stricta leaves might add to the level of salt stress tolerance by maintaining appropriate levels of photosynthesis and normal plant growth as well as by the participation in reactive oxygen species (ROS) production under stress. We speculate that the high expression levels of PPR genes may be dependent on expression levels of their targeted editing genes. Although the results of PPR gene family indicated regulation of a large number of transcripts under salt stress, PPR actions were independent of the salt stress because their RNA editing patterns were unchanged.

Transcriptomic studies reveal a key metabolic pathway contributing to a well-maintained photosynthetic system under drought stress in foxtail millet (Setaria italica L.)

“…Using high-throughput Illumina RNA-seq, Wang et al (2016a) identified and quantified DEGs related to flavonoid biosynthesis in drought-stressed plants. Biosynthesis of brassinosteroids, monoterpenoids, porphyrins, chlorophyll, ubiquinone, and other terpenoid-quinones also is instrumental in adapting plants to drought stress and overcoming stress damage ( Ksouri et al, 2016 ; Hajrah et al, 2017 ; Miao et al, 2017 ). In addition, KEGG pathway analysis indicated a significant enrichment in amino sugar and nucleotide sugar metabolism, and limonene and pinene degradation in response to abiotic stress ( Singh et al, 2017 ; Zhang et al, 2017 ).…”

Dowsing for salinity tolerance related genes in chickpea through genome wide association and in silico PCR analysis

“…Moreover, it has a role in the environmental stress tolerance 144 . The upregulation of TESTA12 was reported in mechanisms of salt stress tolerance in R. stricta 145 and heat stress tolerance 146 .…”

Protective Roles of Cytosolic and Plastidal Proteasomes on Abiotic Stress and Pathogen Invasion

“…Expression of the proteolytic subunit was also upregulated in wheat ( Triticum aestivum ) stems during drought-induced senescence [ 150 , 151 ]. In Rhazya stricta, all genes of the proteolytic subunit ( ClpP ) were upregulated after 12 h of salt stress [ 152 ]. Increased mRNA and protein content of several ClpP isomers also occurred in A. thaliana during long-term cold and high-intensity lighting acclimation [ 122 ], and proteomics revealed that ClpP levels were significantly increased during cadmium stress in tobacco [ 131 ].…”