scholarly journals PIF4-controlled auxin pathway contributes to hybrid vigor in Arabidopsis thaliana

2017 ◽  
Vol 114 (17) ◽  
pp. E3555-E3562 ◽  
Author(s):  
Li Wang ◽  
Li Min Wu ◽  
Ian K. Greaves ◽  
Anyu Zhu ◽  
Elizabeth S. Dennis ◽  
...  
Keyword(s):  
Recurrent Selection ◽  
Leaf Growth ◽  
Hybrid Vigor ◽  
Auxin Biosynthesis ◽  
F1 Hybrids ◽  
Auxin Signaling ◽  
Crop Species ◽  
Altered Expression ◽  
F2 Generation ◽  
Chromosome Segments

F1 hybrids in Arabidopsis and crop species are uniform and high yielding. The F2 generation loses much of the yield advantage and the plants have heterogeneous phenotypes. We generated pure breeding hybrid mimic lines by recurrent selection and also selected a pure breeding small phenotype line. The hybrid mimics are almost completely homozygous with chromosome segments from each parent. Four particular chromosomal segments from C24 and 8 from Ler were present in all of the hybrid mimic lines, whereas in the F6 small phenotype line, the 12 segments were each derived from the alternative parent. Loci critical for promoting hybrid vigor may be contained in each of these 12 conserved segments. We have identified genes with similar altered expression in hybrid mimics and F1 plants but not in the small phenotype line. These genes may be critical for the generation of hybrid vigor. Analysis of transcriptomes indicated that increased expression of the transcription factor PHYTOCHROME-INTERACTING FACTOR (PIF4) may contribute to hybrid vigor by targeting the auxin biosynthesis gene YUCCA8 and the auxin signaling gene IAA29. A number of auxin responsive genes promoting leaf growth were up-regulated in the F1 hybrids and hybrid mimics, suggesting that increased auxin biosynthesis and signaling contribute to the hybrid phenotype. The hybrid mimic seeds had earlier germination as did the seeds of the F1 hybrids, indicating cosegregation of the genes for rosette size and the germination trait. Early germination may be an indicator of vigorous hybrids.

scholarly journals Hybrid mimics and hybrid vigor in Arabidopsis

2015 ◽  
Vol 112 (35) ◽  
pp. E4959-E4967 ◽  
Author(s):  
Li Wang ◽  
Ian K. Greaves ◽  
Michael Groszmann ◽  
Li Min Wu ◽  
Elizabeth S. Dennis ◽  
...  
Keyword(s):  
Metabolic Pathways ◽  
Recurrent Selection ◽  
Hybrid Vigor ◽  
F1 Hybrids ◽  
Parent Plant ◽  
F1 Hybrid ◽  
Altered Expression ◽  
Cell Numbers ◽  
Seed Industry ◽  
Vegetative Biomass

F1 hybrids can outperform their parents in yield and vegetative biomass, features of hybrid vigor that form the basis of the hybrid seed industry. The yield advantage of the F1 is lost in the F2 and subsequent generations. In Arabidopsis, from F2 plants that have a F1-like phenotype, we have by recurrent selection produced pure breeding F5/F6 lines, hybrid mimics, in which the characteristics of the F1 hybrid are stabilized. These hybrid mimic lines, like the F1 hybrid, have larger leaves than the parent plant, and the leaves have increased photosynthetic cell numbers, and in some lines, increased size of cells, suggesting an increased supply of photosynthate. A comparison of the differentially expressed genes in the F1 hybrid with those of eight hybrid mimic lines identified metabolic pathways altered in both; these pathways include down-regulation of defense response pathways and altered abiotic response pathways. F6 hybrid mimic lines are mostly homozygous at each locus in the genome and yet retain the large F1-like phenotype. Many alleles in the F6 plants, when they are homozygous, have expression levels different to the level in the parent. We consider this altered expression to be a consequence of transregulation of genes from one parent by genes from the other parent. Transregulation could also arise from epigenetic modifications in the F1. The pure breeding hybrid mimics have been valuable in probing the mechanisms of hybrid vigor and may also prove to be useful hybrid vigor equivalents in agriculture.

scholarly journals Combining ability and heterosis in plant improvement

2021 ◽  
pp. 108-117
Author(s):  
Begna Temesgen
Keyword(s):  
Genetic Diversity ◽  
Combining Ability ◽  
Crop Improvement ◽  
Critical Factor ◽  
Hybrid Vigor ◽  
Hybrid Breeding ◽  
F1 Hybrids ◽  
Gene Pools ◽  
Crop Species ◽  
Heterotic Groups

Information on combining ability and heterosis of parents and crossings is crucial in breeding efforts. Genetic variety is crucial to the effectiveness of yield improvement efforts because it helps to broaden gene pools in any given crop population. The genotype's ability to pass the intended character to the offspring is referred to as combining ability. As a result, information on combining ability is required to determine the crossing pairs in the production of hybrid varieties. Heterosis is the expression of an F1 hybrid's dominance over its parents in a given feature, as measured not by the trait's absolute value, but by its practical use. To put it another way, heterosis is defined as an increase in the character value of F1 hybrids when compared to the average value of both parents. A plant breeder's ultimate goal is to achieve desirable heterosis (hybrid vigor). In a variety of crop species, heterosis has been widely employed to boost output and extend the adaptability of hybrid types. A crucial requirement for discovering crosses with significant levels of exploitable heterosis is knowledge of the quantity of heterosis in different cross combinations. Any crop improvement program's success is contingent on the presence of a significant level of genetic diversity and heritability. The lack of a broad genetic foundation is the most significant constraint to crop improvement and a major bottleneck in breeding operations. Heterosis is a critical factor in hybrid generation, particularly for traits driven by non-additive gene activity. To get the most out of heterosis for hybrid cultivar production, germplasm must be divided into distinct heterotic groups. Similarly, knowledge on genetic diversity is critical for hybrid breeding and population improvement initiatives because it allows them to analyze genetic diversity, characterize germplasm, and categorize it into different heterotic groupings. In general, general combining ability is used to detect a line's average performance in a hybrid combination, whereas specific combining ability is used to find circumstances where definite combinations perform better or worse than expected based on the mean performance of the lines involved.

scholarly journals Membrane Sterol Composition in Arabidopsis thaliana Affects Root Elongation via Auxin Biosynthesis

2021 ◽  
Vol 22 (1) ◽  
pp. 437
Author(s):  
Meng Wang ◽  
Panpan Li ◽  
Yao Ma ◽  
Xiang Nie ◽  
Markus Grebe ◽  
...  
Keyword(s):  
Root Elongation ◽  
Auxin Transport ◽  
Sterol Composition ◽  
Polar Auxin Transport ◽  
Sterol Biosynthesis ◽  
Auxin Biosynthesis ◽  
Root Tip ◽  
Auxin Signaling ◽  
Auxin Response ◽  
Short Root

Plant membrane sterol composition has been reported to affect growth and gravitropism via polar auxin transport and auxin signaling. However, as to whether sterols influence auxin biosynthesis has received little attention. Here, by using the sterol biosynthesis mutant cyclopropylsterol isomerase1-1 (cpi1-1) and sterol application, we reveal that cycloeucalenol, a CPI1 substrate, and sitosterol, an end-product of sterol biosynthesis, antagonistically affect auxin biosynthesis. The short root phenotype of cpi1-1 was associated with a markedly enhanced auxin response in the root tip. Both were neither suppressed by mutations in polar auxin transport (PAT) proteins nor by treatment with a PAT inhibitor and responded to an auxin signaling inhibitor. However, expression of several auxin biosynthesis genes TRYPTOPHAN AMINOTRANSFERASE OF ARABIDOPSIS1 (TAA1) was upregulated in cpi1-1. Functionally, TAA1 mutation reduced the auxin response in cpi1-1 and partially rescued its short root phenotype. In support of this genetic evidence, application of cycloeucalenol upregulated expression of the auxin responsive reporter DR5:GUS (β-glucuronidase) and of several auxin biosynthesis genes, while sitosterol repressed their expression. Hence, our combined genetic, pharmacological, and sterol application studies reveal a hitherto unexplored sterol-dependent modulation of auxin biosynthesis during Arabidopsis root elongation.

scholarly journals Unravelling the hybrid vigor in domestic equids: the effect of hybridization on bone shape variation and covariation

2019 ◽  
Vol 19 (1) ◽  
Author(s):  
Pauline Hanot ◽  
Anthony Herrel ◽  
Claude Guintard ◽  
Raphaël Cornette
Keyword(s):  
First Generation ◽  
Shape Change ◽  
Morphological Integration ◽  
Hybrid Vigor ◽  
F1 Hybrids ◽  
Shape Variation ◽  
Locomotor System ◽  
Domestic Horses ◽  
Functional Mechanisms ◽  
Underlying Processes

Abstract Background Hybridization has been widely practiced in plant and animal breeding as a means to enhance the quality and fitness of the organisms. In domestic equids, this hybrid vigor takes the form of improved physical and physiological characteristics, notably for strength or endurance. Because the offspring of horse and donkey is generally sterile, this widely recognized vigor is expressed in the first generation (F1). However, in the absence of recombination between the two parental genomes, F1 hybrids can be expected to be phenotypically intermediate between their parents which could potentially restrict the possibilities of an increase in overall fitness. In this study, we examine the morphology of the main limb bones of domestic horses, donkeys and their hybrids to investigate the phenotypic impact of hybridization on the locomotor system. We explore bone shape variation and covariation to gain insights into the morphological and functional expressions of the hybrid vigor commonly described in domestic equids. Results Our data reveal the occurrence of transgressive effects on several bones in the F1 generation. The patterns of morphological integration further demonstrate that the developmental processes producing covariation are not disrupted by hybridization, contrary to functional ones. Conclusions These results suggest that an increase in overall fitness could be related to more flexibility in shape change in hybrids, except for the main forelimb long bones of which the morphology is strongly driven by muscle interactions. More broadly, this study illustrates the interest of investigating not only bone shape variation but also underlying processes, in order to contribute to better understanding how developmental and functional mechanisms are affected by hybridization.

scholarly journals Auxin requirements for a meristematic state in roots depend on a dual brassinosteroid function

2020 ◽  
Author(s):  
M. Ackerman-Lavert ◽  
Y. Fridman ◽  
R Matosevich ◽  
H Khandal ◽  
L. Friedlander ◽  
...  
Keyword(s):  
Signaling Pathways ◽  
Auxin Biosynthesis ◽  
Auxin Signaling ◽  
Critical Ratio ◽  
Dual Effect ◽  
Normal Morphology ◽  
Arabidopsis Root ◽  
Auxin Synthesis ◽  
Meristem Maintenance ◽  
Transcriptional Output

SummaryThe organization of the root meristem is maintained by a complex interplay between plant hormones signaling pathways that both interpret and determine their accumulation and distribution. Brassinosteroids (BR) and auxin signaling pathways control the number of meristematic cells in the Arabidopsis root, via an interaction that appears to involve contradicting molecular outcomes, with BR promoting auxin signaling input but also repressing its output. However, whether this seemingly incoherent effect is significant for meristem function is unclear. Here, we established that a dual effect of BR on auxin, with BR simultaneously promoting auxin biosynthesis and repressing auxin transcriptional output, is essential for meristem maintenance. Blocking BR-induced auxin synthesis resulted in rapid BR-mediated meristem loss. Conversely, plants with reduced BR levels were resistant to loss of auxin biosynthesis and these meristems maintained their normal morphology despite a 10-fold decrease in auxin levels. In agreement, injured root meristems which rely solely on local auxin synthesis, regenerated when both auxin and BR synthesis were inhibited. Use of BIN2 as a tool to selectively inhibit BR signaling, revealed meristems with distinct phenotypes depending on the perturbed tissue; meristem reminiscent of BR-deficient mutants or of high BR exposure. This enabled mapping BR-auxin interactions to the outer epidermis and lateral root cap tissues, and demonstrated the essentiality of BR signaling in these tissues for meristem maintenance. BR activity in internal tissues however, proved necessary to control BR homeostasis. Together, we demonstrate a basis for inter-tissue coordination and how a critical ratio between these hormones determines the meristematic state.

scholarly journals Variability and heritability of some onion (Allium cepa L.) characteristics of parental forms, F1 hybrids and F2 generation

2013 ◽  
Vol 39 (2) ◽  
pp. 293-325 ◽  
Author(s):  
Roch W. Doruchowski
Keyword(s):  
Allium Cepa ◽  
F1 Hybrids ◽  
Skin Thickness ◽  
Male Sterile ◽  
Outer Skin ◽  
Allium Cepa L ◽  
High Heritability ◽  
Heritability Estimates ◽  
F2 Generation

The object of the studies in 1977 was a population of 15 F<sub>1</sub> hybrids, 11 F<sub>2</sub> progenies and 16 parental forms (8 male-sterile A lines and 8 inbred C lines - Table 2). Variability and heritability of some onion characteristic weight, height diameter of the bulbs and their shape, collar thickness, adherence and color of dry outer skin, bulb firmness, shape of the collar and position of root disc) were studied. Variability and heritability estimates of bulb weight, diameter and shape of the collar were relatively high (30-70%).Variability of the skin thickness was also high, but heritability of this trait was low. The lowest variability and heritability were shown for bulb firmness. The high heritability of some traits indicates the possibility of increasing the effects of selection and improvement, especially of the weight and shape of bulbs.

scholarly journals Which Recurrent Selection Scheme To Improve Mixtures of Crop Species? Theoretical Expectations

2019 ◽  
Vol 10 (1) ◽  
pp. 89-107 ◽  
Author(s):  
Jean-Paul Sampoux ◽  
Héloïse Giraud ◽  
Isabelle Litrico
Keyword(s):  
Recurrent Selection ◽  
Genetic Correlations ◽  
Limited Range ◽  
Pure Stand ◽  
Crop Species ◽  
Selection Scheme ◽  
Selection Indices ◽  
Species Mixture ◽  
Set Up ◽  
Two Populations

In a context of increasing environmental challenges, there is an emerging demand for plant cultivars that are adapted to cultivation in species mixture. It is thus pressing to look for the optimization of selection schemes to grow species mixtures, and especially recurrent selection schemes which are at the core of the improvement of many plant species. We considered the case of two populations from different species to be improved by recurrent selection for their performances in mixture. We set up an analytical model of performances in mixture. We expressed the expected responses of the performances in mixture to one cycle of selection in the case of a Reciprocal Mixture Ability selection scheme and of two parallel selection schemes aiming to improve General Mixture Abilities or performances in pure stands. We numerically compared these selection schemes when half-sib or topcross progeny families of selection candidates are tested in mixture. Selection in pure stands appeared efficient within a limited range of genetic correlations between pure stand performance and mixture model effects. The Reciprocal Mixture Ability selection scheme was expected to be less efficient than parallel selections for General Mixture Ability in some situations. The last option enables to control the ratio of expected responses of species contributions to the mixture performance without bias when using selection indices. When more than two species are be improved for their performances in mixture, the advantage of parallel selections for General Mixture Ability is even more marked, providing that compensation trends between species are not too prevalent.

scholarly journals Hormone-regulated defense and stress response networks contribute to heterosis in Arabidopsis F1 hybrids

2015 ◽  
Vol 112 (46) ◽  
pp. E6397-E6406 ◽  
Author(s):  
Michael Groszmann ◽  
Rebeca Gonzalez-Bayon ◽  
Rebecca L. Lyons ◽  
Ian K. Greaves ◽  
Kemal Kazan ◽  
...  
Keyword(s):  
Stress Response ◽  
Pseudomonas Syringae ◽  
Defense Responses ◽  
Gene Activity ◽  
Hybrid Vigor ◽  
Superior Performance ◽  
F1 Hybrids ◽  
Biosynthesis Pathway ◽  
Leaf Cell ◽  
Basal Defense

Plant hybrids are extensively used in agriculture to deliver increases in yields, yet the molecular basis of their superior performance (heterosis) is not well understood. Our transcriptome analysis of a number of Arabidopsis F1 hybrids identified changes to defense and stress response gene expression consistent with a reduction in basal defense levels. Given the reported antagonism between plant immunity and growth, we suggest that these altered patterns of expression contribute to the greater growth of the hybrids. The altered patterns of expression in the hybrids indicate decreases to the salicylic acid (SA) biosynthesis pathway and increases in the auxin [indole-3-acetic acid (IAA)] biosynthesis pathway. SA and IAA are hormones known to control stress and defense responses as well as plant growth. We found that IAA-targeted gene activity is frequently increased in hybrids, correlating with a common heterotic phenotype of greater leaf cell numbers. Reduced SA concentration and target gene responses occur in the larger hybrids and promote increased leaf cell size. We demonstrated the importance of SA action to the hybrid phenotype by manipulating endogenous SA concentrations. Increasing SA diminished heterosis in SA-reduced hybrids, whereas decreasing SA promoted growth in some hybrids and phenocopied aspects of hybrid vigor in parental lines. Pseudomonas syringae infection of hybrids demonstrated that the reductions in basal defense gene activity in these hybrids does not necessarily compromise their ability to mount a defense response comparable to the parents.

Morphology and fitness components of wild × crop F1 hybrids of Sorghum bicolor (L.) in Ethiopia: implications for survival and introgression of crop genes in the wild pool

2013 ◽  
Vol 11 (3) ◽  
pp. 196-205 ◽  
Author(s):  
Asfaw Adugna ◽  
Endashaw Bekele
Keyword(s):  
Risk Assessment ◽  
Natural Hybridization ◽  
Relative Fitness ◽  
F1 Hybrids ◽  
Transgenic Crop ◽  
Fitness Components ◽  
Crop Species ◽  
In The Wild ◽  
Sorghum Bicolor L ◽  
Made In

Natural hybridization between wild/weedy and crop species often results in rare hybrids, which can be more weedy and difficult to control. Moreover, the advent of transgenic crop plants raises questions of biosafety risk assessment on the consequences of rare hybrids with possible fitness enhancing genes on the environment. This study aimed at measuring the fitness components of wild–crop sorghum hybrids for various juvenile survival and adult morphological and fertility characters as part of the risk assessment of transgenic sorghum in Africa where the crop was believed to have first domesticated and serves as the major staple. Out of a pool of hybrids made in 2010 from 23 wild sorghum accessions and two released cultivated sorghum varieties using hand emasculation techniques, seven were selected for the field study of their fitness components in 2011. The study confirmed that crop–wild hybrids of sorghum are fertile. Two approaches were followed (relative fitness and mid-parent heterosis) which showed that most of the hybrids were as fit as their wild parents, and in some cases they showed mid-parent heterosis for the measured traits. The results of this study highlighted a potential risk that hybrids carrying crop genes (including herbicide resistance transgenes) could pose because they could be more weedy than their wild/weedy parents if transgenic sorghum is deployed in regions where the wild and cultivated sorghum populations coexist, such as in Ethiopia and in other parts of Africa.

Patterns of Inheritance in the Bowing Display and Associated Behaviour of Some Hybrid Streptopelia Doves

Behaviour ◽  
1970 ◽  
Vol 36 (3) ◽  
pp. 187-214 ◽  
Author(s):  
S.J.J.F. Davies
Keyword(s):  
The Other ◽  
F1 Hybrids ◽  
Characteristic Form ◽  
Pure Species ◽  
F1 Hybrid ◽  
Cine Film ◽  
F2 Generation ◽  
Species Hybrids ◽  
Relative Variability

AbstractThe bowing display of Streptopelia doves was studied in captive individuals of five species at Madingley, Cambridge, England from 1961 to 1964. The five species were S. roseogrisea-(risoria) (barbary), S. decaocto (collared), S. turtur (turtle), S. chinensis (necklace) and S. senegalensis (senegal). F1 hybrids were bred between the barbary and the other four species and single males of each of the F1 necklace x collared and senegal x turtle were also observed. F2 generation birds of the collared x barbary F1 hybrid, as well as some backcrossed birds were included in the study. Bowing displays were usually given only by male doves when close to another dove. The form of the bowing display differed from species to species and exhibited a typical intensity in each species. Each hybrid also had a bowing display of characteristic form. The ciné film showed that there was variation in form between the bowing cycles of any one bout, both in the pure species and in the hybrids. This variation could not be adequately described from the films taken in this study. The rate of bowing of each species was constant and differed from that of every other species. Hybrids also exhibited a typical intensity in this character. There was much more intra-specific and intra-hybrid variaton in the timing of individual movements within bowing cycles in a bout than in the timing of the bowing cycle as a whole. The relative variability of the different elements could be ranked, and in all species and hybrids studied the timing of the total cycle tended to be least variable and that of the pause at the top of the bow most variable. The frequencies with which bowing displays and kah calls were given under standard conditions, were measured, and provided two other behavioural characters whose pattern of inheritance could be studied. Three patterns of inheritance were found in each of these behaviour patterns of the F1 hybrids. In some cases the behaviour was intermediate between that of the two parents, in others it approximated the behaviour of one parent closely and in others again the hybrid's behaviour exceeded the range of either parent.

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