Plant biomass from different species is heterogeneous, and this diversity in composition can be mined to identify materials of value to fuel and chemical industries. Agave produces high yields of energy-rich biomass, and the sugar-rich stem tissue has traditionally been used to make alcoholic beverages. Here, the compositions of Agave americana and Agave tequilana leaves are determined, particularly in the context of bioethanol production. Agave leaf cell wall polysaccharide content was characterized by linkage analysis, non-cellulosic polysaccharides such as pectins were observed by immuno-microscopy, and leaf juice composition was determined by liquid chromatography. Agave leaves are fruit-like—rich in moisture, soluble sugars and pectin. The dry leaf fiber was composed of crystalline cellulose (47–50% w/w) and non-cellulosic polysaccharides (16–22% w/w), and whole leaves were low in lignin (9–13% w/w). Of the dry mass of whole Agave leaves, 85–95% consisted of soluble sugars, cellulose, non-cellulosic polysaccharides, lignin, acetate, protein and minerals. Juice pressed from the Agave leaves accounted for 69% of the fresh weight and was rich in glucose and fructose. Hydrolysis of the fructan oligosaccharides doubled the amount of fermentable fructose in A. tequilana leaf juice samples and the concentration of fermentable hexose sugars was 41–48 g/L. In agricultural production systems such as the tequila making, Agave leaves are discarded as waste. Theoretically, up to 4000 L/ha/yr of bioethanol could be produced from juice extracted from waste Agave leaves. Using standard Saccharomyces cerevisiae strains to ferment Agave juice, we observed ethanol yields that were 66% of the theoretical yields. These data indicate that Agave could rival currently used bioethanol feedstocks, particularly if the fermentation organisms and conditions were adapted to suit Agave leaf composition.

Flag leaf angle impacts the photosynthetic capacity of densely grown plants and is thus an important agronomic breeding trait for crop architecture and yield. The hormone auxin plays a key role in regulating this trait, yet the underlying molecular and cellular mechanisms remain unclear. Here, we report that two rice (Oryza sativa) auxin response factors (ARFs), OsARF6 and OsARF17, which are highly expressed in lamina joint tissues, control flag leaf angle in response to auxin. Loss-of-function double osarf6 osarf17 mutants displayed reduced secondary cell wall levels of lamina joint sclerenchymatous cells (Scs), resulting in an exaggerated flag leaf angle and decreased grain yield under dense planting conditions. Mechanical measurements indicated that the mutant lamina joint tissues were too weak to support the weight of the flag leaf blade, resembling the phenotype of the rice increased leaf angle1 (ila1) mutant. We demonstrate that OsARF6 and OsARF17 directly bind to the ILA1 promoter independently and synergistically to activate its expression. In addition, auxin-induced ILA1 expression was dependent on OsARF6 and OsARF17. Collectively, our study reveals a mechanism that integrates auxin signaling with the secondary cell wall composition to determine flag leaf angle, providing breeding targets in rice, and potentially other cereals, for this key trait.