Watermelon (Citrullus lanatus) is an economically important horticultural crop.  However, it is susceptible to low-temperature stress, which significantly challenges its production and supply.  Despite the great economic importance of watermelon, little is known about its response to low-temperature stress at the transcriptional level.  In this study, we performed a time-course transcriptome analysis to systematically investigate the regulatory network of watermelon under low-temperature stress.  Six low-temperature-responsive gene clusters representing six expression patterns were identified, revealing diverse regulation of metabolic pathways in watermelon under low-temperature stress.  Analysis of temporally specific differentially expressed genes revealed the time-dependent nature of the watermelon response to low temperature.  Moreover, ClMYB14 was found to be a negative regulator of low-temperature tolerance as ClMYB14-OE lines were more susceptible to low-temperature stress.  Co-expression network analysis demonstrated that ClMYB14 participates in the low-temperature response by regulating the unsaturated fatty acid pathway and heat shock transcription factor.  This study provides substantial information for understanding the regulatory network of watermelon in response to low-temperature stress, and identifies candidate genes for the genetic improvement of watermelon with higher low-temperature tolerance.

Plant height is a key plant architectural trait that affects the seed yield, harvest index and lodging resistance in Brassica napus L., although the genetic mechanisms affecting plant height remain unclear.  Here, a semi-dwarf mutant, df34, was obtained by ethyl methanesulphonate-induced mutagenesis.  Genetic analysis showed that the semi-dwarf phenotype is controlled by one semi-dominant gene, which was located on chromosome C03 using a bulked segregant analysis coupled with whole-genome sequencing, and this gene was named BnaSD.C3.  Then BnaSD.C3 was fine-mapped to a 297.35-kb segment of the “Darmor-bzh” genome, but there was no potential candidate gene for the semi-dwarf trait underlying this interval.  Furthermore, the interval was aligned to the Zhongshuang 11 reference genome.  Finally, combining structural variation analysis, transcriptome sequencing, phytohormone analyses and gene annotation information, BnaC03G0466900ZS and BnaC03G0478900ZS were determined to be the most likely candidate genes affecting the plant height of df34.  This study provides a novel major locus for breeding and new insights into the genetic architecture of plant height in B. napus