miRNAs and their targets regulate plant architecture in Brassica napus

Background: MicroRNAs (miRNAs), a class of non-coding small RNAs, are crucial to the regulation of various developmental processes. Plant architecture is a collection of genetically controlled agronomic traits that determine crop production and mechanized harvesting. Although several genes had been found to regulate plant architecture, the mechanisms whereby miRNAs regulate plant architecture in the rapeseed Brassica napus remain unknown. Results: In this study, we characterized a rod-like rapeseed mutant with an ideal plant architecture that substantially enhanced its breeding potential. To explore miRNAs that contribute to the rapeseed plant architecture, backcross progenies that developed into small plants (rod-like) and tall plants (normal) were used for study. Four small RNA (sRNA) libraries and two degradome libraries from the shoot apex of normal and rod-like plants were sequenced. A total of 925 non-redundant B. napus miRNA precursors were identified, representing 315 precursors for 74 known miRNAs and 610 precursors for 327 novel miRNAs. Expression analysis revealed that 10 known miRNAs and 7 novel miRNAs were differentially expressed between the normal and rod-like plants. In addition, 408 targets were identified through degradome sequencing and 14 targets were further validated via RNA ligase-mediated 5′ rapid amplification of cDNA ends. Furthermore, the functions of miR319 and its target gene TCP4 were studied and provided a novel insight into how miR319 regulates plant architecture. Conclusions: Correlation analysis between differentially expressed miRNAs and their targets demonstrated that nutrition and metal deprivation, energy supply deficiency, senescence and TEOSINTE BRANCHED1/CYCLOIDEA/PCF (TCPs) contributed to the premature termination of shoot development in rod-like mutant. The work further elucidates the mechanism of miRNAs participate in the regulation of plant architecture. small RNA and degradome sequencing in the shoot apex of rod-like and normal B. napus