title: Transcriptome profiling of the spl5 mutant reveals that SPL5 has a negative role in the biosynthesis of serotonin for rice disease resistance.
abstract: BACKGROUND
  Rice mutant, spl5 (spotted leaf 5), has spontaneous hypersensitive-like lesions on its leaves and shows enhanced resistance to pathogens, indicating that SPL5 plays a role in programmed cell death (PCD) and disease resistance. To understand the molecular mechanism of SPL5 gene, we investigated the transcriptome profiles of the spl5 mutant leaves with few lesions (FL) and leaves with many lesions (ML) compared to the wild-type (WT) leaves respectively by microarray.
  
  
  RESULTS
  The data from microarray revealed that 243 and 896 candidate genes (Fold change ≥ 3.0) were up- or down-regulated in the spl5-FL and spl5-ML, respectively, and a large number of these genes involved in biotic defense responses or reactive oxygen species (ROS) metabolism. Interestingly, according to our microarray and real-time PCR assays, the expressions of a transcription factor OsWRKY14 and genes responsible for the biosynthesis of serotonin, anthranilate synthase (AS), indole-3-glycerolphosphate synthase (IGPS), tryptophan synthase (TS) and tryptophan decarboxylase (TDC) were significantly up-regulated in the spl5 mutant. It has been reported previously that TS and TDC expressions are regulated by OsWRKY14 in rice, which raises the possibility that OsWRKY14 regulates serotonin production through the up-regulation of TS and TDC. Our HPLC analysis further confirmed that serotonin levels were higher in the leaves of spl5 mutant than that in WT.
  
  
  CONCLUSIONS
  Since the serotonin plays a critical role in inducing disease-resistance, the increased serotonin level may contribute, at least partly, to the disease resistance in spl5. The SPL5 gene may act as a negative regulatory factor activating the serotonin metabolic pathway, and these results might provide a new insight into the spl5-induced defense response mechanisms in plants.
authors.affiliation: College of Chemistry & Life Sciences, Zhejiang Normal University, Jinhua, 321004 China.
authors.forename: Bin
authors.initials: B
authors.lastname: Jin
authors.affiliation: College of Chemistry & Life Sciences, Zhejiang Normal University, Jinhua, 321004 China.
authors.forename: Xinru
authors.initials: X
authors.lastname: Zhou
authors.affiliation: College of Chemistry & Life Sciences, Zhejiang Normal University, Jinhua, 321004 China.
authors.forename: Baolin
authors.initials: B
authors.lastname: Jiang
authors.affiliation: College of Chemistry & Life Sciences, Zhejiang Normal University, Jinhua, 321004 China.
authors.forename: Zhimin
authors.initials: Z
authors.lastname: Gu
authors.affiliation: College of Chemistry & Life Sciences, Zhejiang Normal University, Jinhua, 321004 China.
authors.forename: Pinghua
authors.initials: P
authors.lastname: Zhang
authors.affiliation: China National Rice Research Institute, Chinese Academy of Agricultural Sciences, Hangzhou, 310006 China.
authors.forename: Qian
authors.initials: Q
authors.lastname: Qian
authors.affiliation: College of Chemistry & Life Sciences, Zhejiang Normal University, Jinhua, 321004 China.
authors.forename: Xifeng
authors.initials: X
authors.lastname: Chen
authors.affiliation: College of Chemistry & Life Sciences, Zhejiang Normal University, Jinhua, 321004 China.
authors.forename: Bojun
authors.initials: B
authors.lastname: Ma
keywords: Disease resistance; Lesion mimic; Microarray; Rice; Serotonin; spl5