Abstract
BackgroundMagnesium (Mg)-deficiency occurs most frequently in strongly acidic, sandy soils. Citrus are grown mainly on acidic and strong acidic soils. Mg-deficiency causes poor fruit quality and low fruit yield in some Citrus orchards. For the first time, we investigated Mg-deficiency-responsive miRNAs in ‘Xuegan’ (Citrus sinensis) roots using Illumina sequencing in order to obtain some miRNAs presumably responsible for Citrus Mg-deficiency tolerance.ResultsWe obtained 101 (69) miRNAs with increased (decreased) expression from Mg-starved roots. Our results suggested that the adaptation of Citrus roots to Mg-deficiency was related to the several aspects: (a) inhibiting root respiration and related gene expression via inducing miR158 and miR2919; (b) enhancing antioxidant system by down-regulating related miRNAs (miR780, miR6190, miR1044, miR5261 and miR1151) and the adaptation to low-phosphorus (miR6190); (c) activating transport-related genes by altering the expression of miR6190, miR6485, miR1044, miR5029 and miR3437; (d) elevating protein ubiquitination due to decreased expression levels of miR1044, miR5261, miR1151 and miR5029; (e) maintaining root growth by regulating miR5261, miR6485 and miR158 expression; and (f) triggering DNA repair (transcription regulation) by regulating miR5176 and miR6485 (miR6028, miR6190, miR6485, miR5621, miR160 and miR7708) expression. Mg-deficiency-responsive miRNAs involved in root signal transduction also had functions in Citrus Mg-deficiency tolerance.ConclusionsWe obtained several novel Mg-deficiency-responsive miRNAs (i.e., miR5261, miR158, miR6190, miR6485, miR1151 and miR1044) possibly contributing to Mg-deficiency tolerance. These results revealed some novel clues on the miRNA-mediated adaptation to nutrient deficiencies in higher plants.
Highlights
Magnesium (Mg)-deficiency occurs most frequently in strongly acidic, sandy soils
Root dry weight (DW) and root and leaf Mg Root DW and root and leaf Mg levels were lower in 0 mM Mg-treated seedlings than in 1 mM Mg-treated ones, and Mg level in leaves from 0 mM Mg-treated seedlings was much less than the sufficient range (Fig. 1) [37]
Illumina sequencing and miRNA annotation Using high-throughput sequencing, we got 20,726,716 (22,139,574) raw reads from sRNA library constructed from control (Mg-deficient) roots
Summary
Magnesium (Mg)-deficiency occurs most frequently in strongly acidic, sandy soils. Magnesium (Mg)-deficiency, a common problem in many agricultural crops, occurs most frequently in strongly acidic, sandy soils, where Mg is very prone to leaching [1]. Citrus are grown mainly on acidic and strong acidic soils and Mg-deficiency is responsible for. It is very important to elucidate the molecular mechanisms on Mg-deficiency impairments and tolerance in higher plants. To our knowledge, such data are rare [10, 12, 13]. The roles of P-deficiencyinduced up-regulation of plant miR399 and miR827 in the maintenance of P homeostasis via inhibiting their targets ubiquitin-conjugating enzyme E2 24 (UBC24) and N limitation adaptation (NLA), respectively have been well characterized [14, 23, 26, 27]
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