Fig. 4.

A hypothetical model to modify grass spikelet structures. In cereals, the spikelet structure unit contains one to three spikelets, where the lateral one is sterile in barley and sorghum. In Brachypodium and wheat, one spikelet contains many florets, whose fertility can be converted for high yield breeding. Phytohormones (BR, JA), TCP (COM, MSD1), AP2 (SvBd1, FZP), HD-Zip (LF1, VRS1, GNI) TFs are involved in specifying SpM identity and fertility. Manipulation of these regulatory modules to increase spikelet number and floret fertility provides a chance to generate optimal inflorescence and spikelet architecture to improve yield. a awn, br bristle, le lemma, f flower, gl glume, LB lateral branch, pa palea, PB primary branch, PS pedicellate spikelet, RA rachis, rg rudimentary glume, SB secondary branch, sl sterile lemma, SP spikelet, SS sessile spikelets