Isolation And Identification Of Magnesium-deficiency-responsive MiRNAs In Citrus Sinensis Roots

Magnesium(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 sequenced two small RNA libraries constructed from Mg-deficient and-sufficient(control)Citrus sinensis roots with Illumina sequencing in order to obtain some miRNAs presumably responsible for citrus Mg-deficiency tolerance.In this study,we obtained 101 up-and 69 down-regulated microRNAs(miRNAs)from Mg-deficient 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 miR394,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 played a role in the adaptation to Mg-deficiency.In conclusion,we identified some new 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 roles of miRNAs in plant adaptation to nutrient deficiencies.