Physiological Basis and Transcriptional Profiling of Three Salt-Tolerant Mutant Lines of Rice

Abstract

Salinity is a complex trait that affects growth and productivity in many crops, including rice. Mutation induction, a useful tool to generate salt tolerant plants, enables the analysis of plants with similar genetic background, facilitating the understanding of the salt tolerance mechanisms. In this work, we generated three salt tolerant mutant lines by irradiation of a salt-sensitive cultivar plants and screened M2 plants at seedling stage in the presence of high salinity. These three lines, SaT20, SaS62, and SaT58, showed different responses to salinity, but exhibited similar phenotype to wild type plants, except SaT20 that displayed shorter height when grown in the absence of salt. Under salt conditions, all three mutants and the parental line showed similar reduction in yield, although relevant differences in other physiological parameters, such as Na+ accumulation in healthy leaves of SaT20, were registered. Microarray analyses of gene expression profiles in roots revealed the occurrence of common and specific responses in the mutants. The three mutants showed up-regulation of responsive genes, the activation of oxido-reduction process and the inhibition of ion transport. The participation of jasmonate in the plant response to salt was evident by down-regulation of a gene coding for a jasmonate O-methyltransferase. Genes dealing with lipid transport and metabolism were, in general, up-regulated except in SaS62, that also exhibited down-regulation of genes involved in ion transport and Ca2+ signal transduction. The two most tolerant varieties, SaS62 and SaT20, displayed lower levels of transcripts involved in K+ uptake. The physiological study and the description of the expression analysis evidenced that the three lines showed different responses to salt: SaT20 showed a high Na+ content in leaves, SaS62 presented an inhibition of lipid metabolism and ion transport and SaT58 differs in both features in the response to salinity. The analysis of these salt tolerant mutants illustrates the complexity of this trait evidencing the breadth of the plant responses to salinity including simultaneous cooperation of alternative or complementary mechanisms.

Whole genome sequence analysis of rice genotypes with contrasting response to salinity stress

“…The DEGs involved in ion transport and homeostasis included potassium channel SKOR (LOC_Os06g14030) and chloride channel protein (LOC_Os04g55210), OsHKT2;3 —Na + transporter (LOC_Os01g34850), ABC transporter, ATP-binding protein (LOC_Os08g30740), AAA family ATPase, (LOC_Os02g19150), calcium-transporting ATPase, plasma membrane-type (LOC_Os12g04220), cation transport regulator-like protein 1 (LOC_Os02g26700), and sulfate transporters (LOC_Os01g41050, LOC_Os03g09970, LOC_Os03g09980). Reduced expression of OsHKT2;4, a high-affinity Na + /K + transporter and SKOR in response to salt stress was previously reported 28 . There were three multi-antimicrobial extrusion (MATE) protein family genes (LOC_Os02g45380, LOC_Os01g31980, LOC_Os10g20350) with role in tolerance to abiotic stresses including salinity 29 .…”

“…Most abundant classes include genes involved in ion transport, oxidative stress tolerance, signal transduction, stress response, and transcriptional regulation (Supplementary Tables S7 and S8 ). Several transcriptomic studies reported involvement of genes associated with these salt tolerance mechanisms 15 , 27 , 28 . The congruence of salt tolerance QTLs with many protein kinase and leucine-rich repeat, zinc-finger, NB-ARC, and P450 domain containing genes was earlier reported 14 .…”

Evaluation of the Saline–Alkaline Tolerance of Rice (Oryza sativa L.) Mutants Induced by Heavy-Ion Beam Mutagenesis

“…The results indicated that heavy-ion beam irradiation can produce high-yield and saline–alkaline-tolerant mutant lines of rice. These results were consistent with those of Domingo, et al [ 48 ], wherein saline–alkaline-tolerant lines with higher yield were isolated through radiation mutagenesis. In this study, PH, SL, SP, and 1000-GW significantly differed among mutant lines ( Table 4 and Table 5 ).…”

Activation-tagging in indica rice identifies a novel transcription factor subunit, NF-YC13 associated with salt tolerance

“…Rice ( Oryza sativa L.) crop is more sensitive to increased soil salinization at seedling and reproductive stages 52 , 53 . Development of salinity tolerant rice varieties is an efficient option to overcome salinity stress and enhance productivity under stress.…”