High frequency DNA rearrangement at qγ27 creates a novel allele for Quality Protein Maize breeding.

Copy number variation (CNV) is a major source of genetic variation and often contributes to phenotypic variation in maize. The duplication at the 27-kDa γ-zein locus (qγ27) is essential to convert soft endosperm into hard endosperm in quality protein maize (QPM). This duplication is unstable and generally produces CNV at this locus. We conducted genetic experiments designed to directly measure DNA rearrangement frequencies occurring in males and females of different genetic backgrounds. The average frequency with which the duplication rearranges to single copies is 1.27 × 10-3 and varies among different lines. A triplication of γ27 gene was screened and showed a better potential than the duplication for the future QPM breeding. Our results highlight a novel approach to directly determine the frequency of DNA rearrangements, in this case resulting in CNV at the qγ27 locus. Furthermore, this provides a highly effective way to test suitable parents in QPM breeding.

The essential role of GhPEL gene, encoding a pectate lyase, in cell wall loosening by depolymerization of the de-esterified pectin during fiber elongation in cotton.

Cotton fiber elongation, largely achieved by cell wall loosening, is an important stage during cotton fiber development. In this present research, a fiber preferential cDNA encoding a pectate lyase (PEL) which could exclusively degrade the de-esterified pectin was isolated from a cotton (Gossypium hirsutum) fiber cDNA library. Subsequently, the corresponding PEL genes were isolated from four different cotton species and characterized. In vitro enzyme assays indicated that GhPEL really exhibited cleavage-activity against de-esterified pectin. The temporal-spatial expression analyses revealed that the GhPEL gene was preferentially expressed in fibers at 10 days-post anthesis (DPA). Antisense GhPEL transgenic cotton plants were generated by Agrobacterium-mediated transformation. Six homozygous lines, each with one or two copies of the transgene inserted as determined by southern blot analysis of the NPTII gene, were selected for further functional analysis. The GhPEL expression during fiber elongation in these transgenic lines was significantly suppressed in various degrees. Furthermore, the reduction of GhPEL enzymatic activity by decreasing GhPEL transcripts severely affected the degradation of de-esterified pectin in primary cell walls of transgenic cotton fibers, which consequently blocked cell wall loosening in early fiber development. Ultimately, the fiber elongation of all these transgenic lines was repressed. These results suggested that GhPEL may play an important role in the process of normal fiber elongation in cotton.