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. 2017 Jul 19;175(1):333–350. doi: 10.1104/pp.17.00719

Figure 4.

Figure 4.

Ectopic expression of MYB26 is unable to induce secondary thickening in the anther in the absence of NST1 or NST2 expression. A, Wild-type plant showing full fertility as evidenced by silique elongation and full seed set. B, nst1nst2 double mutant showing sterility as indicated by a lack of silique elongation; plants also showed increased bushy growth. C, Expression of 35Spro:MYB26 in nst1nst2 background does not rescue male fertility or bushy growth. D, Expression of 35Spro:MYB26 in nst1nst1NST2nst2 background, which is heterozygous for and thus expressing NST2, is fertile, and growth resembles wild type. NST2 acts redundantly with NST1, and the phenotypes of heterozygous lines are equivalent to wild type, with full fertility and normal growth habit (Mitsuda et al., 2005). Boxed regions show increased magnification of the same lines. E to L, Sections stained with phloroglucinol to detect lignin; scale bar represents 50 µm. E Wild-type anther showing secondary thickening in the endothecium. F The nst1nst2 double mutant fails to develop endothecium secondary thickening (arrow). G, Endothecium secondary thickening is not rescued by expression of 35Spro:MYB26 in the nst1nst2 background (arrow). H, Increased levels of anther endothecium thickening were, however, seen with the 35Spro:MYB26 in the nst1nst1Nst2nst2 heterozygous background (arrow). I to L, Secondary thickening in the inflorescence stems (I) wild type, (J) nst1nst2 double mutant (thickening is slightly reduced), and (K) the nst1nst2 double mutant expressing 35Spro:MYB26. L, Ectopic secondary thickening is seen in the inflorescence stem (arrows) when MYB26 is overexpressed in presence of NST2 (35Spro:MYB26 in the nst1nst1NST2nst2 heterozygous background). M, qRT-PCR expression analysis of MYB26, NST1, NST2, and NST3 in the whole inflorescence of wild type, nst1nst2 mutant, nst1nst2 mutant expressing 35Spro:MYB26, and in the nst1 single mutant (nst1nst1NST2nst2 heterozygous line), and nst1nst1NST2nst2 heterozygous line expressing 35Spro:MYB26. N, qRT-PCR expression of genes involved in secondary thickening pathways in the whole inflorescence of various backgrounds shown in M. Error bars represent sd in M and N (t test statistical analysis compared to its relevant background for each line; *P ≤ 0.05; **P ≤ 0.01).