Bolting

Abstract: CONSTANS (CO) promotes flowering of Arabidopsis in response to long photoperiods. Transgenic plants carrying CO fused with the cauliflower mosaic virus 35S promoter (35S::CO) flowered earlier than did the wild type and were almost completely insensitive to length of day. Genes required for CO to promote flowering were identified by screening for mutations that suppress the effect of 35S::CO. Four mutations were identified that partially suppressed the early-flowering phenotype caused by 35S::CO. One of these mutations, suppressor of overexpression of CO 1 (soc1), defines a new locus, demonstrating that the mutagenesis approach is effective in identifying novel flowering-time mutations. The other three suppressor mutations are allelic with previously described mutations that cause late flowering. Two of them are alleles of ft, indicating that FT is required for CO to promote early flowering and most likely acts after CO in the hierarchy of flowering-time genes. The fourth suppressor mutation is an allele of fwa, and fwa soc1 35S::CO plants flowered at approximately the same time as co mutants, suggesting that a combination of fwa and soc1 abolishes the promotion of flowering by CO. Besides delaying flowering, fwa acted synergistically with 35S::CO to repress floral development after bolting. The latter phenotype was not shown by any of the progenitors and was most probably caused by a reduction in the function of LEAFY. These genetic interactions suggest models for how CO, FWA, FT, and SOC1 interact during the transition to flowering.

Abstract: Spinach is an important leafy vegetable enriched with multiple necessary nutrients Here we report the draft genome sequence of spinach (Spinacia oleracea, 2n=12), which contains 25,495 protein-coding genes The spinach genome is highly repetitive with 744% of its content in the form of transposable elements No recent whole genome duplication events are observed in spinach Genome syntenic analysis between spinach and sugar beet suggests substantial inter- and intra-chromosome rearrangements during the Caryophyllales genome evolution Transcriptome sequencing of 120 cultivated and wild spinach accessions reveals more than 420 K variants Our data suggests that S turkestanica is likely the direct progenitor of cultivated spinach and spinach domestication has a weak bottleneck We identify 93 domestication sweeps in the spinach genome, some of which are associated with important agronomic traits including bolting, flowering and leaf numbers This study offers insights into spinach evolution and domestication and provides resources for spinach research and improvement Spinach is an economically important vegetable crop but previous genomic resources were of limited use for comparative and functional analyses Here, Xuet al present a high quality draft spinach genome and transcriptome data for multiple Spinaciaaccessions providing insight into Caryophyllales genome evolution

Abstract: We reported previously that the plant oncogene rolD anticipates and stimulates flowering in Nicotiana tabacum, and encodes ornithine cyclodeaminase, an enzyme catalysing the conversion of ornithine to proline. To investigate on the possible role of proline in flowering, we altered the expression of AtP5CS1, encoding the rate-limiting enzyme of proline biosynthesis in plants. Accordingly we characterized a mutant line containing a T-DNA insertion into AtP5CS1 and introduced in Arabidopsis thaliana AtP5CS1 under the control of the CaMV35S promoter. As expected homozygous p5cs1 mutants behaved as late flowering. In addition p5cs1 mutants exhibited a shorter size and contained lower levels of proline, compared to wild type. 35S-P5CS1 plants, manifested, early in development, overexpression of P5CS1 and accumulation of proline, leading to early flowering, both under long- and short-day conditions. Later in development, down-regulation of P5CS1 occurred in 35S-P5CS1 leaves, leading to proline reduction, and, in turn, impaired bolting and stunted growth. Salt-stress restored expression of P5CS1 and proline accumulation in P5CS1-transformed plants, as well as rescuing growth. Our data suggest that proline plays a key role in flower transition, bolting and coflorescence formation.