Pinoresinol rescues developmental phenotypes of Arabidopsis phenylpropanoid mutants overexpressing .

Most phenylpropanoid pathway flux is directed toward the production of monolignols, but this pathway also generates multiple bioactive metabolites. The monolignols coniferyl and sinapyl alcohol polymerize to form guaiacyl (G) and syringyl (S) units in lignin, components that are characteristic of plant secondary cell walls. Lignin negatively impacts the saccharification potential of lignocellulosic biomass.

H-lignin can be deposited independently of CINNAMYL ALCOHOL DEHYDROGENASE C and D in Arabidopsis.

Lignin contributes substantially to the recalcitrance of biomass toward saccharification. To circumvent this problem, researchers have genetically altered lignin, although, in a number of cases, these efforts have resulted in an undesirable yield penalty. Recent findings have shown that by knocking out two subunits (MED5A and MED5B) of the transcriptional regulatory complex Mediator, the stunted growth phenotype of mutants in p-coumaroyl shikimate 3'-hydroxylase, reduced epidermal fluorescence 8-1 (ref8-1), can be alleviated.

Manipulation of Lignin Monomer Composition Combined with the Introduction of Monolignol Conjugate Biosynthesis Leads to Synergistic Changes in Lignin Structure.

The complexity of lignin structure impedes efficient cell wall digestibility. Native lignin is composed of a mixture of three dominant monomers, coupled together through a variety of linkages. Work over the past few decades has demonstrated that lignin composition can be altered through a variety of mutational and transgenic approaches such that the polymer is derived almost entirely from a single monomer.

Distinct nodule and leaf functions of two different sucrose phosphate synthases in alfalfa.

In alfalfa, the B form of Sucrose phosphate synthase synthesizes sucrose in the leaves while the A form participates in regulatory cycles of synthesis/breakdown of sucrose/starch in the root nodules. Sucrose (Suc) is the major stable product of photosynthesis that is transported to all heterotrophic organs as a source of energy and carbon. The enzyme sucrose phosphate synthase (SPS) catalyzes the synthesis of Suc.

Linking phenylpropanoid metabolism, lignin deposition, and plant growth inhibition.

Lignin, a polymer found in the plant secondary cell wall, is a major contributor to biomass' recalcitrance toward saccharification. Because of this negative impact toward the value of lignocellulosic crops, there is a special interest in modifying the content and composition of this important plant biopolymer. For many years this endeavor has been hindered by the plant growth inhibition that is often associated with manipulations to phenylpropanoid metabolism.

Transgenic alfalfa (Medicago sativa) with increased sucrose phosphate synthase activity shows enhanced growth when grown under N2-fixing conditions.

Overexpression of SPS in alfalfa is accompanied by early flowering, increased plant growth and an increase in elemental N and protein content when grown under N2-fixing conditions. Sucrose phosphate synthase (SPS; EC 2.3.