Evidence from Photosynthetic Characteristics for the Hybrid Origin of Diplotaxis muralis from a C₃‐C₄ Intermediate and a C₃ Species

Abstract

Artificial hybridization studies have been carried out between plants with different photosynthetic types to study the genetic mechanism of photosynthetic types. However, there are only few reports describing the possibility of natural hybridization between plants with different photosynthetic types. A previous cytological and morphological study suggested that a cruciferous allotetraploid species, Diplotaxis muralis (L.) DC. (2n = 42), originated from natural hybridization between D. tenuifolia (L.) DC. (2n = 22) and D. viminea (L.) DC. (2n = 20). These putative parents have recently been reported to be a C (3)-C (4) intermediate and a C (3) species, respectively. If this hybridization occurred, D. muralis should have characteristics intermediate between those of the C (3)-C (4) intermediate and C (3) types. We compared leaf structures and photosynthetic characteristics of the three species. The bundle sheath (BS) cells in D. tenuifolia included many centripetally located chloroplasts and mitochondria, but those of D. viminea had only a few organelles. The BS cells in D. muralis displayed intermediate features between the putative parents. Glycine decarboxylase P protein was confined to the BS mitochondria in D. tenuifolia, but accumulated mainly in the mesophyll mitochondria in D. viminea. In D. muralis, it accumulated in both the BS and the mesophyll mitochondria. Values of CO (2) compensation point and its response to changing light intensity were also intermediate between the putative parents. These data support the theory that D. muralis was created by natural hybridization between species with different photosynthetic types.

Inheritance of C3―C4Intermediate Photosynthesis in Reciprocal Hybrids BetweenMoricandia Arvensis(C3―C4) andBrassica Oleracea(C3) That Differ in Their Genome Constitution

“…We found that the Γ value was highly and negatively correlated with the ratio of centripetally located chloroplasts in the BS cells and with the ratios (BS : M) of mitochondrial size and of labeling density of the GDC P-protein. It is also important to note that complete suppression of the expression of the GDC P-protein in the M cells is not required to reduce Γ, as revealed in our previous studies (Ueno et al, 2003(Ueno et al, , 2006b. Based on the data from the present study and our previous findings (Ueno et al, 2003), the C 3 -C 4 intermediate characteristics generally appear to be inherited in hybrid plants on the basis of the ratio of the parent genomes.…”

“…The antiserum was against the P-protein of GDC isolated from pea leaf mitochondria and was kindly provided by Dr. D. J. Oliver (University of Idaho, Moscow, ID, USA). This antiserum was the same as that used in our previous immunocytochemical studies (Ueno et al, 2003(Ueno et al, , 2006b). The density of labeling for GDC P-protein was determined by counting the gold particles on electron micrographs at 25000 × magnification and calculating the number per unit area (µ m -2 ).…”

Production of Raphanus sativus (C3)-Moricandia arvensis (C3-C4 intermediate) Monosomic and Disomic Addition Lines with Each Parentl Cytoplasmic Background and their Photorespiratory Characteristics

“…The amphidiploid (DtDtRR) had characteristics intermediate between the C 3 -C 4 intermediate (D. tenuifolia, DtDt) and C 3 (R. sativus, RR) parents, the sesquidiploid (DtDtR) had the characteristics close to the C 3 -C 4 intermediate parent and other sesquidiploid (DtRR) had strongly C 3 parent characteristics (Ueno et al, 2003). Such a mode of inheritance in the C 3 -C 4 intermediate and C 3 characteristics has also been demonstrated in the hybrids between Diplotaxis muralis (DtDtDvDv) and its ancestral species D. tenuifolia (DtDt) or D. viminea (DvDv), and in the reciprocal hybrids between M. arvensis and B. oleracea (C 3 ) with various genome constitutions (Ueno et al, 2006;. It is suggested that the constitution ratio of the C 3 -C 4 intermediate genome to the C 3 genome in their hybrids is the most important factor determining the degree of expression of the C 3 -C 4 intermediate characteristics.…”

“…However, the Γ of the auto-and alloplasmic DALs carrying one pair of 'b' M. arvensis chromosomes (RMa-b and MaR-b DALs) was significantly different from that of R. sativus (C 3 ), although that of the auto-and alloplasmic MALs with one 'b' M. arvensis chromosome was not signifi cantly different from that of R. sativus (C 3 ). As the amphidiploid showed a Γ intermediate between that of the C 3 -C 4 intermediate and C 3 parents (Ueno et al, 2003;2006;, the present two DALs (RMa-b and MaR-b DALs) also showed intermediate values. When the constitution ratio of the DALs was considered at the individual chromosome level, the constitution ratio of the C 3 -C 4 intermediate chromosome to the C 3 chromosome was 1:1 because they have one pair of homologous chromosomes of the C 3 -C 4 intermediate (M. arvensis) and the C 3 plant (R. sativus).…”

“…When the constitution ratio of the DALs was considered at the individual chromosome level, the constitution ratio of the C 3 -C 4 intermediate chromosome to the C 3 chromosome was 1:1 because they have one pair of homologous chromosomes of the C 3 -C 4 intermediate (M. arvensis) and the C 3 plant (R. sativus). Based on the results of the present and the previous studies (Ueno et al, 2003;2006;, the C 3 -C 4 intermediate characteristics such as the gasexchange characteristics might be expressed in the hybrid plants on the basis of the constitution ratio of each individual chromosome as well as the parent genomes. Therefore, the DAL would be useful material for investigating the genetic mechanisms of the C 3 -C 4 intermediate characteristics.…”