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Production of β-ketoacyl-CoA, which is catalyzed by 3-ketoacyl-CoA synthase (KCS), is the first step in very long chain fatty acid (VLCFA) biosynthesis. Here we identified 58 KCS genes from Gossypium hirsutum, 31 from G. arboreum and 33 from G. raimondii by searching the assembled cotton genomes. The gene family was divided into the plant-specific FAE1-type and the more general ELO-type. KCS transcripts were widely expressed and 32 of them showed distinct subgenome-specific expressions in one or more cotton tissues/organs studied. Six GhKCS genes rescued the lethality of elo2Δelo3Δ yeast double mutant, indicating that this gene family possesses diversified functions. Most KCS genes with GA-responsive elements (GAREs) in the promoters were significantly upregulated by gibberellin A3 (GA). Exogenous GA3 not only promoted fiber length, but also increased the thickness of cell walls significantly. GAREs present also in the promoters of several cellulose synthase (CesA) genes required for cell wall biosynthesis and they were all induced significantly by GA3 . Because GA treatment resulted in longer cotton fibers with thicker cell walls and higher dry weight per unit cell length, we suggest that it may regulate fiber elongation upstream of the VLCFA-ethylene pathway and also in the downstream steps towards cell wall synthesis.

We assembled a total of 297,239 Gossypium hirsutum (Gh, a tetraploid cotton, AADD) expressed sequence tag (EST) sequences that were available in the National Center for Biotechnology Information database, with reference to the recently published G. raimondii (Gr, a diploid cotton, DD) genome, and obtained 49,125 UniGenes. The average lengths of the UniGenes were increased from 804 and 791 bp in two previous EST assemblies to 1,019 bp in the current analysis. The number of putative cotton UniGenes with lengths of 3 kb or more increased from 25 or 34 to 1,223. As a result, thousands of originally independent G. hirsutum ESTs were aligned to produce large contigs encoding transcripts with very long open reading frames, indicating that the G. raimondii genome sequence provided remarkable advantages to assemble the tetraploid cotton transcriptome. Significant different distribution patterns within several GO terms, including transcription factor activity, were observed between D- and A-derived assemblies. Transcriptome analysis showed that, in a tetraploid cotton cell, 29,547 UniGenes were possibly derived from the D subgenome while another 19,578 may come from the A subgenome. Finally, some of the in silico data were confirmed by reverse transcription polymerase chain reaction experiments to show the changes in transcript levels for several gene families known to play key role in cotton fiber development. We believe that our work provides a useful platform for functional and evolutionary genomic studies in cotton.

G2 pea exhibits an apical senescence delaying phenotype under short-day (SD) conditions; however, the structural basis for its apical development is still largely unknown. In the present study, the apical meristem of SD-grown G2 pea plants underwent a transition from vegetative to indeterminate inflorescence meristem, but the apical meristem of long-day (LD)-grown G2 pea plants would be further converted to determinate floral meristem. Both SD signal and GA(3) treatment enhanced expression of the putative calcium transporter PPF1, and pea homologs of TFL1 (LF and DET), whereas LD signal suppressed their expression at 60 d post-flowering compared with those at 40 d post-flowering. Both PPF1 and LF expressed at the vegetative and reproductive phases in SD-grown apical buds, but floral initiation obviously increased the expression level of PPF1 compared with the unchanged expression level of LF from 40 to 60 d post-flowering. In addition, although the floral initiation significantly enhanced the expression levels of PPF1 and DET, DET was mainly expressed after floral initiation in SD-grown apical buds. Therefore, the main structural difference between LD- and SD-grown apical meristem in G2 pea lies in whether their apical indeterminate inflorescence meristem could be converted to the determinate structure.

Senescence is the process of programmed degradation. The G2 line of pea exhibits apical senescence-delaying phenotype under short-day (SD) conditions, but the mechanism regulating the apical senescence is still largely unknown. Gibberellin (GA) was proved to be able to delay this apical senescence phenotype in G2 pea grown under long-day (LD) conditions. Here we show that the initiation of cell death signals in the terminal floral meristem was involved in the regulation of apical senescence in pea plants. SD signals prevented the formation of the cell death region in the apical mersitem. Moreover, GA3 treatment could effectively inhibit the occurrence of cell death-mediated apical senescence in LD-grown apical buds. Therefore, our data suggest that the prevention of apical senescence in SD-grown G2 pea through GA3 treatment may be largely responsible for the regulation of occurrence of the DNA fragmentation in apical meristem.

Production of β‐ketoacyl‐CoA, which is catalyzed by 3‐ketoacyl‐CoA synthase (KCS), is the first step in very long chain fatty acid (VLCFA) biosynthesis. Here we identified 58 KCS genes from Gossypium hirsutum, 31 from G. arboreum and 33 from G. raimondii by searching the assembled cotton genomes. The gene family was divided into the plant‐specific FAE1‐type and the more general ELO‐type. KCS transcripts were widely expressed and 32 of them showed distinct subgenome‐specific expressions in one or more cotton tissues/organs studied. Six GhKCS genes rescued the lethality of elo2Δelo3Δ yeast double mutant, indicating that this gene family possesses diversified functions. Most KCS genes with GA‐responsive elements (GAREs) in the promoters were significantly upregulated by gibberellin A3 (GA). Exogenous GA3 not only promoted fiber length, but also increased the thickness of cell walls significantly. GAREs present also in the promoters of several cellulose synthase (CesA) genes required for cell wall biosynthesis and they were all induced significantly by GA3. Because GA treatment resulted in longer cotton fibers with thicker cell walls and higher dry weight per unit cell length, we suggest that it may regulate fiber elongation upstream of the VLCFA‐ethylene pathway and also in the downstream steps towards cell wall synthesis.

Germination is the first and maybe the foremost growth stage in the life cycle of a plant. Herein, we report that initiation of germination in the Arabidopsis Columbia ecotype was accompanied by a sharp decrease in the amount of extractable total RNA. At the beginning of our germination experiment, we were usually able to obtain 35–40 μg total RNA from 100 mg dry seeds. However, after 3 d of cold stratification, we could only obtain less than 5 μg total RNA from the same amount of starting material. Young seedlings contained approximately 100 μg total RNA per 100 mg fresh tissue. Further studies showed that inhibition of de novo RNA synthesis by actinomycin D prevented the degradation of parental RNA and, in the meantime, significantly delayed the germination process. Several ribonuclease-like genes that were highly expressed in dry seeds, and especially during the cold stratification period, were discovered. We propose that these enzymes are involved in the regulation of parental RNA degradation. These results indicate that parental RNA metabolism may be an important process for Arabidopsis seed germination. (Managing editor: Ya-Qin Han)

Proteomic analysis was performed on seedlings after different light treatments. A total of (1 350±31) protein spots was separated and visualized on each silver nitrate-stained two-dimensional gel using protein samples prepared from light-grown or etiolated seedlings with or without 6–9 h light treatment. Twenty-five protein spots (encoded by 19 genes) that were significantly accumulated upon light treatment were identified using the matrix-assisted laser desorption ionization time-of-flight mass spectrometry method. Functional proteomics indicated that these proteins involved mainly in chloroplast development, energy metabolism, cell cycle progression and membrane electron transport. For 18 of the protein-coding genes we identified through an internet search, the transcript levels of 17 genes matched roughly with their protein content in etiolated and green seedlings, suggesting that these genes were regulated by light mainly at the transcriptional level. Despite a very significant increase in the amount of proteins upon light treatment, similar RNA levels were found in dark-grown or green seedlings for the carbonic anhydrase gene At3g05100, indicating a possible post-transcriptional regulatory mechanism. Elucidation of light-induced protein accumulation will undoubtedly enhance our understanding of plant photomorphogenesis. (Managing editor: Ya-Qin Han)

Using a degenerative probe designed according to the most conservative region of a known Lys- and His-specific amino acid transporter (LHT1) from Arabidopsis, we isolated a full-length cDNA named OxHT(histidine transporter of Oryza sativa L.) by screening the rice cDNA library. The cDNA is 1.3 kb in length and the open reading frame encodes for a 441 amino acid protein with a calculated molecular mass of 49 kDa. Multiple sequence alignments showed that OsHT shares a high degree of sequence conservation at the deduced amino acid level with the Arabidopsis LHT1 and six putative lysine and histidine transporters. Computational analysis indicated that OsHT is an integral membrane protein with 11 putative transmembrane helices. This was confirmed by the transient expression assay because the OsHT-GFP fusion protein was, indeed, localized mainly in the plasma membrane of onion epidermal cells. Functional complementation experiments demonstrated that OsHT was able to work as a histidine transporter in Saccharomyces cerevisiae, suggesting that OsHT is a gene that encodes for a histidine transporter from rice. This is the first time that an LHT-type amino acid transporter gene has been cloned from higher plants other than Arabidopsis. ( Managing editor: Li-Hui ZHAO)

We assembled a total of 297,239 Gossypium hirsutum (Gh, a tetraploid cotton, AADD) expressed sequence tag (EST) sequences that were available in the National Center for Biotechnology Information database, with reference to the recently published G. raimondii (Gr, a diploid cotton, DD) genome, and obtained 49,125 UniGenes. The average lengths of the UniGenes were increased from 804 and 791 bp in two previous EST assemblies to 1,019 bp in the current analysis. The number of putative cotton UniGenes with lengths of 3 kb or more increased from 25 or 34 to 1,223. As a result, thousands of originally independent G. hirsutum ESTs were aligned to produce large contigs encoding transcripts with very long open reading frames, indicating that the G. raimondii genome sequence provided remarkable advantages to assemble the tetraploid cotton transcriptome. Significant different distribution patterns within several GO terms, including transcription factor activity, were observed between D- and A-derived assemblies. Transcriptome analysis showed that, in a tetraploid cotton cell, 29,547 UniGenes were possibly derived from the D subgenome while another 19,578 may come from the A subgenome. Finally, some of the in silico data were confirmed by reverse transcription polymerase chain reaction experiments to show the changes in transcript levels for several gene families known to play key role in cotton fiber development. We believe that our work provides a useful platform for functional and evolutionary genomic studies in cotton.

Senescence, a sequence of biochemical and physiological events, constitutes the final stage of development in higher plants and is modulated by a variety of environmental factors and internal factors. PPF1 possesses an important biological function in plant development by controlling the Ca2+ storage capacity within chloroplasts. Here we show that the expression of PPF1 might play a pivotal role in negatively regulating plant senescence as revealed by the regulation of overexpression and suppression of PPF1 on plant development. Moreover, TFL1, a key regulator in the floral repression pathway, was screened out as one of the downstream targets for PPF1 in the senescence-signaling pathway. Investigation of the senescence-related phenotypes in PPF1(-) tfl1-1 and PPF1(+) tfl1-1 double mutants confirmed and further highlighted the relation of PPF1 with TFL1 in transgenic plants. The activation of TFL1 expression by PPF1 defines an important pathway possibly essential for the negative regulation of plant senescence in transgenic Arabidopsis.