Effects of Dietary Resistant Starch on the Wnt Signaling Pathway and Preneoplastic Cells in the Colons of Azoxymethane-Treated Rats.

Dietary resistant starch (RS) has been suggested to reduce colonic neoplasia. To determine the effects of digestion-resistant cornstarch on colonic carcinogenesis and Wnt signaling in azoxymethane (AOM)-treated F344 rats, diets containing naturally occurring RS from corn lines derived partially from Guat209 (GUAT), AR16035 (AR), or a hybrid (ARxGUAT), containing 34.5 ± 2.0, 0.2 ± 0.1, and 1.9 ± 0.1% RS, respectively, were fed at 55% of the diet. GUAT-fed rats had increased cecal content and tissue weight and decreased cecal pH compared with AR- or ARxGUAT-fed rats. Numbers of aberrant crypt foci (ACF) were not different among diet groups. Increased numbers of crypts/focus were observed in AOM-injected rats fed GUAT compared with rats fed other diets. ß-catenin mRNA expression of the crypts was significantly increased in GUAT-fed rats injected with AOM relative to those injected with saline. These findings suggest that selected dietary RSs may at some level further enhance colonocyte proliferation and differentiation in an AOM-treated colon.

Phenotypic and Transcriptional Analysis of Divergently Selected Maize Populations Reveals the Role of Developmental Timing in Seed Size Determination.

Seed size is a component of grain yield and an important trait in crop domestication. To understand the mechanisms governing seed size in maize (Zea mays), we examined transcriptional and developmental changes during seed development in populations divergently selected for large and small seed size from Krug, a yellow dent maize cultivar. After 30 cycles of selection, seeds of the large seed population (KLS30) have a 4.7-fold greater weight and a 2.6-fold larger size compared with the small seed population (KSS30). Patterns of seed weight accumulation from the time of pollination through 30 d of grain filling showed an earlier onset, slower rate, and earlier termination of grain filling in KSS30 relative to KLS30. This was further supported by transcriptome patterns in seeds from the populations and derived inbreds. Although the onset of key genes was earlier in small seeds, similar maximum transcription levels were observed in large seeds at later stages, suggesting that functionally weaker alleles, rather than transcript abundance, may be the basis of the slow rate of seed filling in KSS30. Gene coexpression networks identified several known genes controlling cellularization and proliferation as well as novel genes that will be useful candidates for biotechnological approaches aimed at altering seed size in maize and other cereals.