Biophysical parameters related to gibberellin (GA)-dependent stem elongation were examined in dark-grown stem-length genotypes of Pisum sativum L. The rate of internode expansion in these genotypes is altered due to recessive mutations which affect either the endogenous levels of, or response to, GA. The GA deficient dwarf L181 (ls), two GA insensitive semierectoides dwarfs NGB5865 and NGB5862 (Ika and Ikb, respectively) and the `slender' line L197 (la cry[ill]), which is tall regardless of GA content, were compared to the wild-type tall cultivar, Torsdag. Osmotic pressure, estimated by vapor pressure osmometry, and turgor pressure, measured directly with a pressure probe, did not correlate with the differences in growth rate among the genotypes. Mechanical wall properties of frozen-thawed tissue were measured using a constant force assay. GA deficiency resulted in increased wall stiffness judged both on the basis of plastic compliance and plastic extensibility normalized for equal stem circumference. Plastic compliance was not reduced in the GA insensitive dwarfs, though Ika reduced circumference-normalized plasticity. In contrast, in vivo wall relaxation, determined by the pressure-block technique, differed among genotypes in a manner which did correlate with extension rates. The wall yield threshold was 1 bar or less in the tall lines, but ranged from 3 to 6 bars in the dwarf genotypes. The results with the ls mutant indicate that GA enhances stem elongation by both decreasing the wall yield threshold and increasing the wall yield coefficient. In the GA-insensitive mutants, Ika and Ikb, the wall yield threshold is substantially elevated. Plants possessing Ika may also possess a reduced wall yield coefficient.
The gibberellin (GA) biosynthesis mutants lh‐1 and lh‐2 have been used to examine the physiological role of GAs in pea seed development. The LH protein is required for the three‐step oxidation of ent ‐kaurene to ent ‐kaurenoic acid early in the GA biosynthesis pathway. The allele‐specific interaction of lh‐1 and lh‐2 with chemical inhibitors of these three steps suggests that LH encodes the multi‐functional GA biosynthesis enzyme ent ‐kaurene oxidase. Unlike the lh‐2 mutation which reduces seed weight and decreases seed survival by ∼50% compared with wild‐type plants, the lh‐1 allele has a transient effect on embryo and seed growth and only slightly increases seed abortion. These seed phenotypes parallel the effects of the two mutant alleles on GA levels in young seeds. Detailed examination of the growth of lh‐1 seeds reveals homeostatic regulation of GA‐promoted embryo and seed growth. Although GA‐deficient seeds grow more slowly than WT seeds, decreased assimilate availability to the developing seeds is not the primary reason for the altered seed development. Instead, GAs act to promote some process(es) required for embryo and seed growth and only indirectly influence the distribution of assimilates. How GA deficiency causes seed abortion is not known but it may simply be a consequence of reduced seed or embryo growth rate. These results demonstrate that even relatively small changes in the levels of GAs in young seeds can alter seed development and suggest that the available GA‐related mutants may represent only a subset of all possible mutants with reduced GA levels or GA signalling.
Conventional methods of dietary assessment are prone to recall bias and place burden on participants.Our aim was to compare the performance of image-based dietary assessment (IBDA), including food photography (FP) and video recording (VR), with the criterion of weighed food records (WFR).In this comparative study, participants captured meals using FP and VR before and after consumption, over 2 days. Food type and portion size were assessed using the images and videos. Energy and nutrient intakes (mean of 2 days) were compared against WFR.Eighty-four healthy adults (mean [standard deviation] age = 29 [8] years), recruited through advertisement in Glasgow, UK, between January and August 2016 were enrolled in the study. Eighty participants (95%) (mean [standard deviation] age = 28 [7] years) completed the study and were included in the analysis.Agreement in estimated energy and nutrient intake between WFR and IBDA. The IBDA method feasibility was evaluated using a questionnaire. Inter-rater and intra-rater reliability were assessed.The performance of the IBDA methods against WFR and their inter and intra-rater reliability were tested with Bland-Altman plots and Spearman correlations. Intra-class agreement between methods was assessed using κ statistics.Inter-rater reliability was strong for both IBDA methods in estimating energy intake (ρ-coefficients: FP = 0.80; VR = 0.81). There was no difference in the agreement between the 2 assessors. Intra-rater reliability was high. FP and VR underestimated energy intake by a mean (95% agreement limits) of -13.3% (-56.4% and 29.7%) and -4.5% (-45.5% and 36.4%), respectively. IBDA demonstrated moderate-to-strong correlations in nutrient intake ranking, median ρ-coefficients for all nutrients: FP = 0.73 (interquartile range, 0.09) and VR = 0.82 (interquartile range, 0.02). Inter-class agreement of IBDA methods was moderate compared with the WFR in energy intake estimation. IBDA was more practical and enjoyable than WFR.IBDA and VR in particular demonstrated a moderate-to-strong ability to rank participants' dietary intake, and considerable group and inter-class agreement compared with the WFR. However, IBDA was found to be unsuitable for assessment in individuals.
Summary Brassinosteroids (BRs) are growth‐promoting plant steroid hormones, and in garden pea ( Pisum sativum L.), the lka mutant is defective in BR perception. Here, we show that LKA encodes P. sativum BRI1 (PsBRI1), a homolog of BRI1, which is the Arabidopsis leucine‐rich repeat receptor‐like kinase/BR receptor. PsBRI1 was isolated by screening a pea cDNA library using Arabidopsis BRI1 cDNA as the probe. PsBRI1 is predicted to encode a 1188‐amino‐acid protein that has 78% similarity with Arabidopsis BRI1. Sequence analysis of PsBRI1 in the lka mutant led to the identification of a missense mutation that converts the highly conserved aspartic acid residue to asparagine, which is located in the leucine‐rich repeat, just before the island domain that may bind BR or a BR–protein complex. The mutation identified in PsBRI1 co‐segregated with the semi‐erectoide lka phenotype. Transcript analysis of LKA / PsBRI1 indicates that it is ubiquitously expressed in pea and that the expression was downregulated by exogenous BR. The lka mutant was then utilized in further studies to analyze the independent actions of BR and gibberellin (GA) through the characterization of BR response on GA mutants and GA response on BR mutants.
In the garden pea ( Pisum sativum L.), shoots of the extremely short plants with the mutant na (phenotype nana) are found by bioassay to contain undetectable levels of gibberellin‐like substances. This is confirmed by the use of near isogenic lines differing at the Na locus. Thus, mutant na appears to block a step early in the pathway of gibberellin synthesis. It is suggested that the polar gibberellin‐like substance found in the apical portion of shoots of tall ( Le ) but not dwarf ( le ) peas could be GA 1 . Extracts of shoots of na Le peas treated with GA 20 (the major active gibberellin in dwarf peas) possess a large amount of GA 1 ‐like activity whereas extracts of shoots of na le peas treated with GA 20 possess a much reduced amount. Thus, gene Le may allow the conversion of a less active gibberellin (GA 20 ) into one more active in stimulating elongation in the pea (the GA 1 ‐like compound). In contrast to their influence in the shoot, the na and Le genes do not appear to be operative in controlling the gibberellin content of developing seed, indicating that organ specific gibberellin biosynthesis and metabolism occur in peas.
Abstract The pea (Pisum sativum) homolog, PsKO1, of the Arabidopsis GA3 gene was isolated. It codes for a cytochrome P450 from the CYP701A subfamily and has ent-kaurene oxidase (KO) activity, catalyzing the three step oxidation of ent-kaurene to ent-kaurenoic acid in the gibberellin (GA) biosynthetic pathway when expressed in yeast (Saccharomyces cerevisiae). PsKO1 is encoded by the LH gene because in three independent mutant alleles, lh-1, lh-2, and lh-3, PsKO1 has altered sequence, and the lh-1 allele, when expressed in yeast, failed to metabolize ent-kaurene. The lh mutants of pea are GA deficient and have reduced internode elongation and root growth. One mutant (lh-2) also causes a large increase in seed abortion. PsKO1 (LH) is expressed in all tissues examined, including stems, roots, and seeds, and appears to be a single-copy gene. Differences in sensitivity to the GA synthesis inhibitor, paclobutrazol, between the mutants appear to result from the distinct nature of the genetic lesions. These differences may also explain the tissue-specific differences between the mutants.
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