The involvement of NtFtsZ2-1 gene in the regulation of chloroplast division and expansion in tobacco.

Chloroplasts are a vital group of organelles of plants, yet the molecular mechanisms associated with their division remain poorly understood. Recent studies have revealed that the FtsZ protein, known as a key component in prokaryotic cell division, is involved in chloroplast division process. The NtFtsZ2-1 gene was isolated from Nicotiana tabacum by RT-PCR, and the sense and antisense expression plasmids were used to examine the function of NtFtsZ2-1 gene in transgenic tobacco. Light and confocal observations revealed that the normal chloroplast division process was severely disrupted in transgenic plants with enhanced or reduced expression of NtFtsZ2-1 gene. These chloroplasts were abnormally larger in size and fewer in number compared with that of the wild-type tobacco. But the total chloroplast plan area per mesophyll cell was conserved in sense, antisense and wild type tobaccos. Analyses of electron micrographs and chlorophyll content of different transgenic plants showed that constitutively enhancing or inhibiting the expression of NtFtsZ2-1 gene had no direct influence on the ultrastructure and photosynthetic ability of chloroplasts. Basing on these results, we suggest that NtFtsZ2-1 gene is involved in chloroplast division and expansion; the fluctuation of NtFtsZ2-1 expression level would alter normal chloroplast number and size in plant cells. In addition, the similarities of ultrastructure and photosynthetic ability of chloroplasts among sense, antisense and wild type tobaccos implies that a special mechanism regulate the relationship between chloroplast number and size to maximize photosynthetic rate.

[Alteration of protein and amino acid components and Rubisco activity in leaves of thermo-sensitive mutant line of rice during induced of green and yellow banding].

We have determined the Rubisco components and activity, whole leaf protein and amino acid components of thermo-sensitive mutant line 1103s of rice (Oryza sativa ssp. indica) leaves during induces green and yellow banding in this study. The results are as follows: The structure and components of Rubisco in the mutant are the same as in the wild form and relatively stable, but the activity of the mutant Rubisco greatly changes as a special protein of molecular weight 56.2 kD (PI=4.5) appears and disappears. When the green-yellow bands appear, the special protein disappears, and the activity of the mutant-rice Rubisco decreases, whereas when the green-yellow bands in the same part of the leaves disappear, the special protein appears and the activity of Rubisco is increase. The above shows the changes of the activity of the mutant-rice Rubisco during photosynthesis are closely related to the special protein in the leaves and its structure and components, and possibly to the regulating protein of Rubisco. The protein particularly regulates metabolic processes of amino acids preventing regulation of the preceding amino acids, such that the formation of the structural material in chloroplast is prevented, and finally the chloroplast thylakoid structure degenerates.