Leaf cDNA-AFLP analysis of two citrus species differing in manganese tolerance in response to long-term manganese-toxicity

Abstract

BackgroundVery little is known about manganese (Mn)-toxicity-responsive genes in citrus plants. Seedlings of ‘Xuegan’ (Citrus sinensis) and ‘Sour pummelo’ (Citrus grandis) were irrigated for 17 weeks with nutrient solution containing 2 μM (control) or 600 μM (Mn-toxicity) MnSO4. The objectives of this study were to understand the mechanisms of citrus Mn-tolerance and to identify differentially expressed genes, which might be involved in Mn-tolerance.ResultsUnder Mn-toxicity, the majority of Mn in seedlings was retained in the roots; C. sinensis seedlings accumulated more Mn in roots and less Mn in shoots (leaves) than C. grandis ones and Mn concentration was lower in Mn-toxicity C. sinensis leaves compared to Mn-toxicity C. grandis ones. Mn-toxicity affected C. grandis seedling growth, leaf CO2 assimilation, total soluble concentration, phosphorus (P) and magenisum (Mg) more than C. sinensis. Using cDNA-AFLP, we isolated 42 up-regulated and 80 down-regulated genes in Mn-toxicity C. grandis leaves. They were grouped into the following functional categories: biological regulation and signal transduction, carbohydrate and energy metabolism, nucleic acid metabolism, protein metabolism, lipid metabolism, cell wall metabolism, stress responses and cell transport. However, only 7 up-regulated and 8 down-regulated genes were identified in Mn-toxicity C. sinensis ones. The responses of C. grandis leaves to Mn-toxicity might include following several aspects: (1) accelerating leaf senescence; (2) activating the metabolic pathway related to ATPase synthesis and reducing power production; (3) decreasing cell transport; (4) inhibiting protein and nucleic acid metabolisms; (5) impairing the formation of cell wall; and (6) triggering multiple signal transduction pathways. We also identified many new Mn-toxicity-responsive genes involved in biological and signal transduction, carbohydrate and protein metabolisms, stress responses and cell transport.ConclusionsOur results demonstrated that C. sinensis was more tolerant to Mn-toxicity than C. grandis, and that Mn-toxicity affected gene expression far less in C. sinensis leaves. This might be associated with more Mn accumulation in roots and less Mn accumulation in leaves of Mn-toxicity C. sinensis seedlings than those of C. grandis seedlings. Our findings increase our understanding of the molecular mechanisms involved in the responses of plants to Mn-toxicity.

Leaf cDNA-AFLP analysis reveals novel mechanisms for boron-induced alleviation of aluminum-toxicity in Citrus grandis seedlings

“…Guo et al (2014) reported that B-toxicity induced the expression of ABC transporter G family 40 in 'Sour pummelo' leaves. However, the expression of two ABC transporter genes (i.e., TDFs #62-1 and 127-2) was detected only in ÀAl leaves (Table 1), which agrees with the results obtained on Mn-toxic 'Sour pummelo' leaves (Zhou et al, 2013). showed that upregulation of an Mg transporter gene OsMGT1 was required for conferring rice Al-tolerance.…”

“…qRT-PCR analysis was performed according to Zhou et al (2013). There were three biological replicates and two technical replicates for each treatment.…”

“…Total RNA was extracted using Recalcitrant Plant Total RNA Extraction Kit (Bioteke Corporation, China) according to manufacturer's instructions. cDNA synthesis and cDNA-AFLP analysis were performed according to Zhou et al (2013).…”

cDNA-AFLP analysis reveals the adaptive responses of citrus to long-term boron-toxicity

“…Overexpression of OsCBSX4 improved tobacco plant tolerance to salinity, oxidative, and heavy metal stresses [43]. We observed that B-toxicity decreased the transcript level of CDCP (TDF #251_3) in C. sinensis leaves (Table 2), as obtained on manganese (Mn)-toxic C. grandis leaves [44]. However, B-deficient C. sinensis roots had higher level of CBS family protein [45].…”

Differential expression of genes in purple‐shoot tea tender leaves and mature leaves during leaf growth

“…There were three biological replicates. cDNA synthesis, purification and cDNA‐AFLP analysis were performed according to Zhou et al …”