Chromosome number, pairing relationship and meiotic behavior were evaluated in 24 Brazilian accessions of different Paspalum species as an initial screening to determine which of them might be useful in an interspecific hybridization program. The analysis showed that six were diploids, 16 tetraploids and two hexaploids. The pairing relationship was typical for the ploidy level and agreed with reported data. However, the meiotic behavior after diakinesis was much more abnormal than expected considering the pairing relationship. There was a high frequency of abnormal tetrads in the majority of accessions.

Paspalum notatum is a forage grass recognized as one of the major constituents of the native grasslands in the New World. The knowledge of the genetic diversity and structure of P. notatum populations is fundamental for the conservation and germplasm management of this species. About 11 microsatellite markers were isolated from P. notatum and characterized in 25 accessions. The average number of alleles per locus was 7.9 and the PIC ranged from 0.36 to 0.89. The data demonstrated that the most of markers are suitable to detect polymorphism and to study the genetic diversity in the P. notatum species. Moreover, the transferability of these microsatellite were tested on other three congeneric species.

No abstract

The gamma-zeins are a mixture of 16, 27, and 50-kDa polypeptides which are important in the formation and stabilization of protein bodies (PB). These organelles are used for deposition of zeins, the water-insoluble storage proteins in maize. The nature of the physical interaction between proteins in the assembly and stabilization of PB are fairly well known. It is suggested the repeated hexapeptide sequence (PPPVHL)(8) in the N-terminus is responsible for aggregation of the gamma-zeins on the PB surface. Despite this importance, there is little information about the native conformation of gamma-zeins. In this work, we have analyzed the secondary structures of gamma-zeins in purified protein bodies from two maize cultivars, in the solid state, by FTIR and NMR spectroscopy. The results revealed that gamma-zeins in their physiological state are comprise similar proportions of alpha-helix and beta-sheet, 33 and 31% as determined by FTIR. It was not possible to state if the polyproline II (PPII) conformation is present in the solid-state structure of gamma-zeins, as has been demonstrated for the hexapeptide in solution. Because of the similarity of the solid-state NMR spectra of gamma and alpha-zeins in the alpha carbon region we attributed their contributions to the beta-sheet structures rather than to the PPII conformation or a mixture of these extended structures.

The proline-rich N-terminal domain of gamma-zein has been reported in relevant processes, which include its ability to cross the cell membranes. Evidences indicate that synthetic hexapeptide (PPPVHL), naturally found in N-terminal portion of gamma-zein, can adopt the polyproline II (PPII) conformation in aqueous solution. The secondary structure of gamma-zein in maize protein bodies had been analyzed by solid state Fourier transform infrared and nuclear magnetic resonance spectroscopies. However, it was not possible to measure PPII content in physiological environment since the beta-sheet and PPII signals overlap in both solid state techniques. Here, the secondary structure of gamma-zein has been analyzed by circular dichroism in SDS aqueous solution with and without ditiothreitol (DTT), and in 60% of 2-propanol and water with DTT. The results show that gamma-zein has high helical content in all solutions. The PPII conformation was present at about 7% only in water/DTT solution.