Figure 7: Induction of GhSWEET genes in different cotton–Xcm interactions.

(a) GhSWEET10 induction by Avrb6 in protoplasts of the resistant line Acb6 and the susceptible line Ac44E. Graph displays Avrb6-induced GhSWEET10 reads per kilobase of transcript per million mapped reads and fold change from RNA-Seq analysis with Ac44E (compatible) and Acb6 (incompatible) cotton lines. (b) qRT–PCR analysis of GhSWEET10 in Ac44E and Acb6 plants upon Xcm infections. Two-week-old cotyledons were syringe-inoculated with different Xcm strains at OD₆₀₀=0.1 and tissues were collected at 24 hpi. GhUBQ1 was used as an internal control. The data are shown as mean±s.d. (n=3) from three independent repeats. (c) Transactivation assay of pGhSWEET10D::LUC from Acb6 and Ac44E in response to Avrb6 in cotton protoplasts. The promoter of GhSWEET10D was amplified from Acb6 and Ac44E, respectively, and fused with luciferase reporter. Protoplasts of cotton variety FM706V were co-transfected with the reporter construct and Avrb6 or an empty vector control (Ctrl). The data are shown as mean±s.d. (n=3) from three independent repeats. An asterisk indicates the significant difference using two-tailed t-test (P<0.05) between two reporter constructs after Avrb6 induction. (d) Induction of clade III GhSWEET genes by different Xcm isolates. Two-week-old cotyledons were syringe-inoculated with different Xcm isolates (Xcm1-Xcm9) collected from different locations in Texas, USA at OD₆₀₀=0.1. Tissues were collected at 24 hpi. GhUBQ1 was used as an internal control for qRT–PCR analysis. The data are shown as mean±s.d. (n=3) from three independent repeats. An asterisk indicates significant difference using two-tailed t-test (P<0.01) compared to the water control. The above experiments were repeated three times with comparable results.