Klebsormidium flaccidum genome reveals primary factors for plant terrestrial adaptation.

The colonization of land by plants was a key event in the evolution of life. Here we report the draft genome sequence of the filamentous terrestrial alga Klebsormidium flaccidum (Division Charophyta, Order Klebsormidiales) to elucidate the early transition step from aquatic algae to land plants. Comparison of the genome sequence with that of other algae and land plants demonstrate that K. flaccidum acquired many genes specific to land plants. We demonstrate that K. flaccidum indeed produces several plant hormones and homologues of some of the signalling intermediates required for hormone actions in higher plants. The K. flaccidum genome also encodes a primitive system to protect against the harmful effects of high-intensity light. The presence of these plant-related systems in K. flaccidum suggests that, during evolution, this alga acquired the fundamental machinery required for adaptation to terrestrial environments.

Identification of a Sed5-like SNARE gene LjSYP32-1 that contributes to nodule tissue formation of Lotus japonicus.

We identified a Sed5-like clone LjSYP32-1 which contributes to nodule tissue formation and plant growth in Lotus japonicus. In the L. japonicus expressed sequence tag (EST) clone databases of Kazusa DNA Research Institute, another syntaxin-related clone (LjSYP32-2) was also detected, and the nucleotide and amino acid sequences of these two clone are very similar to each other. Real-time PCR and promoter analysis indicated that expression of LjSYP32-1 was dominant compared with LjSYP32-2 in the various plant organs. Promoter analysis and in situ hybridization revealed that LjSYP32-1 was expressed significantly in the inner cortex cell layer surrounding the infected zone of young nodules and in the meristem area of developing lateral root. To explore the function and physiological role of LjSYP32-1 in nodules and other plant organs, stable transformation lines of L. japonicus expressing either sense or antisense LjSYP32-1 were prepared. The antisense plants showed a significantly retarded plant growth phenotype, suggesting a role for LjSYP32-1 in supporting plant growth. In the same transgenic lines, the plants were capable of forming nodules, but the acetylene reduction activity was reduced by around 50% per plant. The nodules were much smaller and some nodules were fused to each other by sharing the inner cortex. The rate of occurrence of such irregular nodules was twice that observed in wild-type plants. The data suggest that LjSYP32-1 contributes to the support of plant growth and normal nodule tissue differentiation.