Agronomic potential and seed composition of cuphea, an annual crop for lauric and capric seed oils

Structurally divergent lysophosphatidic acid acyltransferases with high selectivity for saturated medium chain fatty acids from Cuphea seeds

Lysophosphatidic acid acyltransferase (LPAT) catalyzes acylation of the sn-2 position on lysophosphatidic acid by an acyl CoA substrate to produce the phosphatidic acid precursor of polar glycerolipids and triacylglycerols (TAGs). In the case of TAGs, this reaction is typically catalyzed by an LPAT2 from microsomal LPAT class A that has high specificity for C18 fatty acids containing Δ9 unsaturation. Because of this specificity, the occurrence of saturated fatty acids in the TAG sn-2 position is infrequent in seed oils. To identify LPATs with variant substrate specificities, deep transcriptomic mining was performed on seeds of two Cuphea species producing TAGs that are highly enriched in saturated C8 and C10 fatty acids. From these analyses, cDNAs for seven previously unreported LPATs were identified, including cDNAs from Cuphea viscosissima (CvLPAT2) and Cuphea avigera var. pulcherrima (CpuLPAT2a) encoding microsomal, seed-specific class A LPAT2s and a cDNA from C. avigera var. pulcherrima (CpuLPATB) encoding a microsomal, seed-specific LPAT from the bacterial-type class B. The activities of these enzymes were characterized in Camelina sativa by seed-specific co-expression with cDNAs for various Cuphea FatB acyl-acyl carrier protein thioesterases (FatB) that produce a variety of saturated medium-chain fatty acids. CvLPAT2 and CpuLPAT2a expression resulted in accumulation of 10:0 fatty acids in the Camelina sativa TAG sn-2 position, indicating a 10:0 CoA specificity that has not been previously described for plant LPATs. CpuLPATB expression generated TAGs with 14:0 at the sn-2 position, but not 10:0. Identification of these LPATs provides tools for understanding the structural basis of LPAT substrate specificity and for generating altered oil functionalities.

Cytogenetics off interpopulation Cuphea lanceolata hybrids

Cuphea lanceolata Ait. (Lythraceae) is an annual diploid (x = 6) with medium-chain fatty acid rich seed oils. Wild C. lanceolata populations are classified as C. lanceolata f. silenoides or C. lanceolata f. lanceolata on the basis of flower pigment differences. Although these taxa are taxonomically close, their interfertility has not been demonstrated. We describe meiotic phenomena underlying the sterility of hybrids between C. lanceolata f. silenoides (LNS-43) and C. lanceolata f. lanceolata (LNC-78) populations. We assayed metaphase and anaphase I microsporocytes of the parent and hybrid populations. The hybrids were female and male sterile. The mean percentage of stainable pollen was 94.9% for the parents and 1.1% for the hybrids. Chromosomes paired and disjoined normally in the parents (LNS-43 and LNC-78) and abnormally in the hybrids (LNS-43 x LNC-78 and LNC-78 x LNS-43). Univalents, unequal chromosome distributions, and laggards were observed in the hybrids. The mean number of univalents per cell was 0.00 for the parents and 5.95 for the hybrids, the mean number of bivalents per cell was 6.00 for the parents and 1.51 for the hybrids, and the mean number of chiasmata per cell was 9.19 for the parents and 4.04 for the hybrids. The most frequently observed (75%) anaphase I chromosome distribution for the hybrids was 7:5:0 (pole-pole-laggards). The genome affinities of the hybrids were half those of the parents (a mean of 0.5 for the hybrids as opposed to 1.0 for the parents). Although C. lanceolata f. silenoides and C. lanceolata f. lanceolata freely hybridize, their progeny are sterile, and the genetic diversity of LNC-78, and perhaps of C. lanceolata f. lanceolata as a whole, cannot be accessed through hybrids with C. lanceolata f. silenoides or C. viscosissima.

Restriction fragment length polymorphism and allozyme linkage map of Cuphea lanceolata

Cuphea lanceolata Ait. has had a significant role in the domestication of Cuphea and is a useful experimental organism for investigating how medium-chain lipids are synthesized in developing seeds. To expand the genetics of this species, a linkage map of the C. lanceolata genome was constructed using five allozyme and 32 restriction-fragment-length-polymorphism (RFLP) marker loci. These loci were assigned to six linkage groups that correspond to the six chromosomes of this species. Map length is 288 cM. Levels of polymorphism were estimated for three inbred lines of C. lanceolata and an inbred line of C. viscosissima using 84 random genomic clones and two restriction enzymes, EcoRI and HindIII. Of the probes 29% detected RFLPs between C. lanceolata and C. viscosissima lines. Crosses between these species can be exploited to expand the map.

Cuphea: a new plant source of medium-chain fatty acids

The plant genus Cuphea (family Lythraceae) promises to provide a new source of industrially and nutritionally important medium-chain fatty acids, especially of lauric acid now supplied exclusively by coconut and palm kernel oils from foreign sources. The seed lipids of Cuphea were first discovered in the 1960s to contain high percentages of several medium-chain fatty acids, including caprylic, capric, lauric, and myristic acid. Research is still in the early stages, but it is intensifying toward the goal of developing the genus into a new temperate climate crop for production of specialty oils. Given the diversity of Cuphea seed lipid composition and the wide ecological and distributional range of the genus, it may be possible to tailor crops to produce selected fatty acids on demand under a variety of growing conditions. Cuphea comprises about 260 species, most native to the New World tropics. Its morphology, classification, chromosome numbers, distribution, ecology, and folk uses are presented. Seed structure is described and seed lipid composition for 73 species is summarized. Problems in domestication and agronomic progress are reviewed. Knowledge of the biosynthetic mechanism controlling the lipids produced by Cuphea remains very limited. Future research in this area, and particularly successful employment of gene transfer techniques, may allow genes controlling the mechanism to be transferred to an already established seed oil producer such as rapeseed. Presently, both traditional plant breeding techniques and newer biotechnological methods are directed toward Cuphea oilseed development.