Fig. 6.
Models depicting the molecular basis of Verticillium wilt and salt stress tolerance in G. thurberi and G. davidsonii. a Phenotypic comparison of G. thurberi (D1) and G. raimondii (D5) seedlings (35-day-old seedlings) in response to challenge with Verticillium dahliae. Photographs were taken under normal conditions or 14 days after challenge with Verticillium dahliae. b Heat maps for differentially expressed genes with annotations related to salicylic acid (SA) signaling, NB-LRR, and WRKYs. Genes with an adjusted P value < 0.05 and an absolute value of log2[foldchange] > 1 found by EdgeR were designated as differentially expressed. c A proposed model showing that the SA signaling pathways enhance Verticillium wilt tolerance in G. thurberi. V. dahliae attack induces SA biosynthesis via the isochorismate synthase (ICS) and phenylalanine ammonia-lyase (PAL) pathways in plastids. Enhanced disease susceptibility (EDS1) and phytoalexin deficient 4 (PAD4) are required for increased SA accumulation. SA methyltransferase (SAMT) catalyzes SA to MeSA, which diffuses into the cytoplasm, where it is converted back to active SA by SABP2. The red and blue digits in brackets represent the upregulated genes in D1 and D5, respectively. d Phenotypic comparison of G. davidsonii (D3) and G. thurberi (D1) seedlings in response to salt stress treatment (250 mM NaCl watering 21-day-old seedlings every 2 days). Photographs were taken under normal conditions or 14 days after treatment with NaCl solution. e Heat maps for differentially expressed genes with annotations related to ABA, ethylene, and CBL-CIPK pathways. Genes with an adjusted P value < 0.05 and an absolute value of log2[foldchange] > 1 found by EdgeR were designated as differentially expressed. f Transcriptional network related to salt response in G. raimondii and G. davidsonii. Ethylene biosynthesis, calcium signaling, and vacuole NHX are activated in G. davidsonii. The NCED3 gene encodes the enzyme which catalyzes the first step of ABA biosynthesis. The ABA signaling pathway, comprising PYR/PYL/RCAR, PP2C, and SnRKs proteins, is a major plant hormone involved in salt stress responses. Ethylene biosynthesis is catalyzed by the SAM, ACS (ACC synthase), and ACO (ACC oxidase) enzymes. The ethylene signaling pathway includes ethylene receptor, CTR1, and EIN2. TPK (two-pore potassium) is K+ channel that trafficks K+ out of the vacuole. NHX1 (tonoplast-based Na+/H+ exchanger) is required for sequestration of excessive Na+ and Cl− in the vacuole. The red and blue digits in the brackets represent the upregulated genes in D3 and D5, respectively