Analysis Of P-protein Genes Of Glycine Decarboxylase Between Moricandia Nitens And Brassica Crops

As one of important oilcrops, rapeseed belongs to the Brassica genus Cruciferae family. Being the C3 species, Brassica crops have a very high photorespiratory rate, and then have very low photosynthesis efficiency. With an intermediate CO2 compensation pcint between C3 and C4, Moricandia nitens is one of a C3-C4 intermediate species of Cruciferae and very close to Brassica crops. C3-C4 species is usually regarded as an important material for improving carbon utility of C3 crops since it is more close to C3 crops than C4 species. It is believed that differential localization of decarboxylation and carboxylation in association with Kranz anatomy distinguishes species with C4 or C3-C4 intermediate photosynthesis from species with C3 photosynthesis. Being a bridge material, sesquitetraploid (MACC) was produced in our lab. Under this condition, one copy of M genome became coexistent with one copy of A genome that allowed for allosyndesis between them and inereasing the probability to transfer C3-C4 character into A genomes. In order to introduce the C3-C4 character from M. nitens into diploid Brassica crops, subsequently, these sesquitetraploids (MACC) were choosed to sexual cross with B. rapa (AA) and the offspring that phenotypes are more similar to B. rapa could be selected to get rid of the suppression from the two copies of CC genomes as much as possible. And it is very possible to obtain a new type of B. rapa that contains heterogenic fragments of M. nitens in each of the two A homologous chromosomes and to eliminate the repression of C3 background. Meanwhile, it is still unknown why the P-protein of glycine decarboxylase was absent from the mesophelly cell of C3-C4 species compare to C3 species. Then, some research works were carried out and all the results in this study are as follow:1. The total of 2,966 bp and 3,254 bp sequences of gdcP contained 1323 bp and 1608 bp of the 5'-untranslated region and regulatory region respectively, the first and second exons and introns, and very small part of the third exon were isolated from M. nitens and B. napus, respectively, and deposited in the Genbank under the accession number AY544771 and AY544772.2. While exons show the smallest variation, the largest diversity was revealed in the transcript-regulatory region with a few conserved islands. Although each of the three transcriptional parts from M. nitens and B. napus always grouped together, the regulatory regions from the two C3 species, Arabidopsis and B.napus, classed into one group and showed considerable differenes from the C3-C4 species. It indicated that Arabidopsis diverged earlier than the divergence between Moricandia and Brassica, and the main difference between C3-C4 and C3 species was lie in the transcriptionary region.3. Established a procedure of Agrobacterium-medidted transformation of C3-C4 species Moricandia arvensis.4. The promoter-contained 1.6 kb sequence of B. napus was fused with GUS and the chimeric gene transformed another C3-C4 species, M. arvensis. GUS was detected mainly in the vascular tissue as well as in mesophyll cells in the leaves of transgenic plants. It implied that trans-acting elements determining mesophyll-specific expression for gdcP gene is conserved in both C3 and C3-C4 species. However, the cis-acting elements changed in C3-C4 Moricandia species during evolution process.5. In this study, a specific marker^ named gdcPM, was derived from the defined gene itself, in particularly from the highly divergent regulatory region between C3 and C3-C4 species, to aid the subsequent introduction of C3-C4 photosynthesis from M. nitens into Brassica crops. The results showed it to be a dominant marker, being present in M. niters and the somatic hybrids, but absent in six cultivars of B. napus. Since it is dominant in nature, this gene-specific marker may also be important in helping to screen recombinant lines among the MACC sesquitetraploids since screening for CO2 compensation point measurement is a laborious task, especially in the selection of recessive alleles such as the C3-C4 type of gdcP.6. One offspring named 1H75-1 between MACC and Brassica rapa with a Kranz-like leaf anatomy was screened out. SSR and cytological results indicated that this hybrid was really a recombinant between M-genome from Moricandia nitens and A from Brassica; The measurement results of CO? compensation point indicated, only with a Kranz-like leaf anatomy but without the specific distribution of an active P-protein as Morincandia nitens, 1H75-1 had a very close point to C3 Brassica species, and it implied that both the Kranz-like leaf anatomy and the specific distribution of an active P-protein are essential for the low CO2 compensation point of C3-C4 species.