COMPARATIVE BIOCHEMICAL STUDY OF TWO ALLELIC FORMS OF A GENE AFFECTING LEAF-SHAPE IN THE TOMATO

Through successive selfing of lanceolate, a leaf-shape mutant in the tomato, the 3 leaf-shape forms, namely, normal (La⁺/La⁺), lanceolate (La⁺/La), and homozygous lanceolate (La/La), were obtained in a uniform genetic background. The mutant allele lanceolate causes the increase in activities of the following oxidative enzymes: tyrosinase, laccase, peroxidase and catalase. The lanceolate gene exhibits a dosage effect with respect to these enzymes; the homozygous lanceolate shows the highest activity, heterozygous lanceolate is intermediate, and normal shows the lowest activity. The relative differences in activity of these enzymes between the 3 genotypes persist at all stages of development and in all organs examined.     

Evidence for a revertant at the La locus in regenerating hypocotyl segments in tomato

Summary Leafy and leafless phenotypes were regenerated in vitro from hypocotyl segments of leafless forms (reduced and modified) of the homozygous lanceolate (La) mutant in tomato. Segregation of progeny of leafy regenerates into homozygous. mutant (La La), heterozygote (La La ⁺) and normal (La ⁺ La ⁺) indicates that cells forming the shoot apical meristems undergo a genetic reversion, and that the nutrient medium might be selecting for the heterozygote. Among the progeny of the regenerates is a true breeding, unlobed variant. Leaves of the variant are pinnately compound and the margins are entire. Opposite cotyledons followed in development by two simple leaves before the appearance of a pinnately compound leaf with an occasional lanceolate-shaped leaflet suggests that the unlobed variant is morphologically intermediate between La La ⁺ and La ⁺ La ⁺.     

PHENYLBORIC ACID,A CHEMICAL AGENT SIMULATING THE EFFECT OF THE LANCEOLATE GENE IN THE TOMATO

Lanceolate, a spontaneously occurring mutant in the tomato, which has 1 dosage of the mutant gene, causes a change in the shape of the leaf from the odd-pinnately compound leaf characteristic of the normal tomato plant to a simple, much-reduced in size lanceolate leaf. Homozygous mutant plants, which have 2 dosages of the mutant gene, exhibit extreme lanceolate features, producing a simple narrow leaf, similar in shape to the lanceolate leaf but much smaller in size. The mutant allele of the lanceolate gene causes, in addition to the change in leaf form, the increase in activities of the following oxidative enzymes: tyrosinase, laccase, peroxidase and catalase. The lanceolate gene exhibits a dosage effect with respect to these enzymes, homozygous lanceolate showing the highest activity; heterozygous lanceolate, an intermediate; and normal, the lowest activity. Treatment of germinating normal tomato seeds with phenylboric acid simulated the effect of the mutant allele of the lanceolate gene with regard to both the induction of a lanceolate leaf and the increase in the activity of the above 4 oxidative enzymes; phenylboric acid treatment resulted in relatively higher increase in the activities of the oxidative enzymes in normal and heterozygous lanceolate than in homozygous lanceolate. A direct and close relationship existed between the shape of the leaf and the activity of the enzymes during leaf development. It is suggested that the mutant allele of the lanceolate gene, as well as phenylboric acid, induces an increase in activity of the oxidative enzymes and that this increase in enzyme activities brings about the orderly change in form.     

DOSAGE EFFECTS OF THE LANCEOLATE GENE IN TOMATO

In contrast to the odd-pinnately compound leaf of the normal (+/+) tomato plant (Lycopersicon esculentum), the single-gene mutant lanceolate (La/+) generally has a simple leaf. Lanceolate plants, also, have small fruits and flowers, weak apical dominance, and exhibit variation in the position and fusion of cotyledons. Homozygous mutants (La/La) appear in 3 different phenotypes, 1 of which, narrow, has narrow simple leaves, sterile inflorescences, and extremely weak apical dominance. The other 2, modified, and reduced, lack an organized shoot. After selfing La/ + plants for 9 generations, autotetraploids were produced with the aid of colchicine. In addition, several triploid plants arose spontaneously. The study of diploid, triploid, and tetraploid material with various proportions of the La allele revealed in many characters a graded series as a function of the La dosage. With increasing La dose, there was a gradual reduction in: (1) total leaf length; (2) the number and size of primary and secondary lateral leaflets; (3) the number and size of marginal lobes of the terminal leaflet, associated with an increase in the proportional length of the terminal leaflet. Many leaves were found with the basal lobes of the terminal leaflet resembling incompletely separated lateral leaflets. The differences in leaf shape between different genotypes came about before the leaf primordium was 3 mm long. There was a progressive delay in the initiation of lateral primordia with increasing La dosage. It is proposed that the gradual changes from compound to simple leaves with increasing La dosage are produced by successively greater restrictions of meristematic activity after the terminal leaflet is formed. With increasing proportion of La alleles, the reproductive structures showed: (1) a decrease in the number of flowers per inflorescence; (2) a decrease in the length of the sepals; (3) an increase in the proportion of flowers with dialytic anthers. Dialytic anthers had narrow adaxial lobes and were frequently twisted along their main axes. The common denominator for most trends affected by the La allele seems to be a general reduction of growth, but more so in lateral than in longitudinal growth. Histological data suggest that the reduction in lateral growth is mainly brought about by a reduction of cell division in lateral meristems.     

Morphogenetic effect of phenylboric acid on various leaf-shape mutants in the tomato, duplicating the effect of thelanceolate gene

Summary Treatment of germinating tomato seeds ofnormal (La ⁺/La ⁺),lanceolate (La ⁺/La) and several other leaf-shape mutants with phenylboric acid (PBA) duplicates the action of theLa gene with respect to the following: 1) Causes an increase in the level of activity of the four oxidative enzymes tyrosinase, laccase, peroxidase and catalase; 2) causes a corresponding change in leaf form; 3) shows a concentration effect similar to the dosage effect exhibited by theLa gene with respect to both the increase in the activity of oxidative enzymes and a change in leaf form; 4) causes changes, when applied to plants carrying any of several leaf-shape mutants, similar to those caused by theLa gene when the latter is in combination with these leaf shape mutant genes. Based on previous evidence and the current evidence, it is suggested that the primary action of PBA as well as of theLa gene, is to cause the increase in the level of activity of the four oxidative enzymes and the latter in turn, among other factors, determine the shape and size of the leaf in the tomato.     

Pleiotropic morphological and abiotic stress resistance phenotypes of the hyper-abscisic acid producing Abo™ mutant in the periwinkleCatharanthus roseus

The pleiotropic properties of aabo abo (Abo^™) γ-ray induced mutant ofCatharanthus roseuscv. Nirmal, selected among the M₂ generation seeds for ability to germinate at 45°C, are described. The mutant produced seeds possessing tricotyledonous embryos, unlike the typically dicotyledonous embryos present in the wild type Abo⁺ seeds. In comparison to Abo⁺ adults, the mutant plants had short stature and lanceolate leaves. The vascular bundles in the leaves and stem were poorly developed. Leaf surfaces were highly trichomatous, epidermal, cortex and mesophyll cells were small sized and a large majority of stomata were closed. Besides high temperature, the mutant was salinity and water-stress tolerant. The abscisic acid (ABA) content in the leaves was about 500-fold higher. The genetic lesionabo responsible for the above pleiotropy was recessive and inherited in Mendelian fashion. The seedlings and adult plants of the mutant accumulated higher proline than Abo⁺ plants. The phenotypes ofabo abo mutants permitted the conclusions that (i) the mutant synthesizes ABA constitutively, (ii) both ABA-dependent and ABA independent pathways for proline and betaine accumulation are functional in the mutant, and (iii) cell division, elongation and differentiation processes in embryo and adult plant stages are affected in the mutant.     

MORPHOGENETIC ASPECTS OF A LEAFLESS MUTANT IN TOMATO I. GENERAL PATTERNS IN DEVELOPMENT

The embryo of the reduced form of the lanceolate mutant in tomato fails to undergo the heart-shaped stage of development. Cells in the shoot apical region of this leafless mutant lose their meristematic character and develop into mature parenchyma during embryogenesis. This early loss of meristem tissue leads to the determinate growth which is evident in the seedling. In contrast to normal, starch grains are visible with the light microscope in cells of the shoot tip of the mutant hypocotyl from early embryogeny up to and including the seedling stage, and protein bodies are abundant in the same tissue of fully developed mutant embryos. The shoot apical region in homozygous mutant embryos with cotyledons or cotyledon-like structures exhibits some cytochemical and morphological similarity with the normal shoot apex. Morphological variation in these forms appears to be in a continuous pattern. The extent of their development and consequent longevity is related to possible differences in rates of cell expansion and variation in environmental factors during the early stages of embryogenesis.     

航天诱变凤仙花SP2代形态变异的研究

对经“神舟4号”卫星搭载后的SP2代凤仙花的形态变异进行了研究。结果表明:子叶数目除有了两片的外,尚有三片和四片的。子叶形态上出现连生子叶、杯状子叶和大小不等子叶。真叶的形态上出现线状披针形,其小孢子母细胞减数分裂不正常,小孢子不育。花的结构上出现花瓣增多和花的叶化现象。茎的分枝上,有的不分枝,仅具主茎,有的分枝多达40枝以上。这些变化对研究和认识航天诱变育种有一定的理论和实际的意义。     

Effect of water stress on transport of [2-14C]abscisic acid in intact plants ofPhaseolus coccineus L.

Summary Eight- to 10-day-old plants ofPhaseolus coccineus, which grow on vermiculite with a water content of 12–17% of the water-holding capacity, stop growing completely, whereas water potential and relative water content are almost unaffected. [2-¹⁴C]Abscisic acid, which is applied to the midrib of a primary leaf, is transported especially to the roots and the apical bud, but not to the second primary leaf and the cotyledons. Water-stressed plants, however, export only negligible amounts of ABA from the donor leaf to the plant. Thus an accumulation of ABA occurs in the donor leaf. Consequently water stress can increase ABA concentration in leaves not only by stimulating ABA synthesis but also by inhibiting ABA transport. Recovery of growth and ABA transport after reirrigation is very weak. Water stress has no effect on ABA metabolism in bean plants.Abbreviations ABA abscisic acid - GA gibberellic acid - IAA indoleacetic acid - RWC relative water content in plants - TLC thin-layer chromatography     

Regulation of Leaf Shape in the Solanifolia Mutant of Tomato (Lycopersicon esculentum) by Plant Growth Substances

The solanifolia mutant (sf/sf) of tomato (Lycopersicon esculentum)produces leaves consisting of leaflets with entire margins,unlike the lobed leaflets of normal plants. Normal plants treatedwith gibberellic acid (GA₃) produced leaves with entire marginswhereas mutant plants exposed to 2-chloroethyl-trimethyl ammoniumchloride (CCC)—an inhibitor of gibberellin biosynthesis—producedlobing of leaflets. The leaf area of the mutant was significantlygreater than that of the normal, but was not significantly differentfrom GA₃-treated normal leaves. Similarly, in CCC-treated mutantleaves the leaf area was not different from that of normal untreatedleaves. These observations suggest that the sf/sf mutation affectsthe leaf shape through its effect on endogenous gibberellinsand/or inhibitory substances. Leaf shape, Lycopersicon esculentum, plant growth substances, tomato     

A nuclear mutation blocking initiation of the lamina in leaves of Nicotiana syhestris

Isolation of a nuclear recessive mutation (lam-1) blocking initiation of the lamina in leaves of Nicotiana sylvestris Speg. et Comes is described. Histological analysis of the mutant apex demonstrates a defect in establishment of meristematic activity along the margins of emerging primordia, the earliest cytological event in lamina formation. Mutant leaves grow to their normal length (about 30 cm) but fail to expand. Transverse sections show that mutant leaves are essentially naked midribs, lacking the characteristic cell types of the wild-type mesophyll. In the absence of lateral expansion, all secondary veins develop along the longitudinal axis, producing abnormal parallel venation. The mutant is defective in phase transition and grows indefinitely as a juvenile vegetative rosette. Exogenous gibberellic acid induces rapid stem elongation and flowering, but does not correct the lamina defect, indicating that juvenile arrest is a pleiotropic consequence of a gibberellin deficiency in bladeless leaves. The calyx, corolla and gynoecium in mutant flowers show defects in lateral development, indicating that the lam-1 gene plays a crucial role in development of floral organs as well as leaves.Abbreviations GA gibberellin - GA₃ gibberellic acid - WT wildtype The technical assistance of Regan Perry is gratefully acknowledged.     

Potential of bioinsecticidal Bacillus thuringiensis inoculum to suppress gray mold in tomato based on induced systemic resistance

The potential of the active ingredient of a commercial bioinsecticide, XenTari^® (Bacillus thuringiensis [BT] serovar aizawai strain ABTS‐1857), to suppress gray mold in tomato plants was elucidated. First, a suspension of the active ingredient of XenTari^® and a liquid culture of the bacterial strain as BT inocula were sprayed onto detached leaves or drenched into pots of tomato seedlings, and then, propagules of the gray mold fungus, Botrytis cinerea, were inoculated onto the leaves. The gray mold disease was significantly suppressed when rhizospheres were drenched with either inoculum, but not when inocula were sprayed onto detached leaves of seedlings. Both BT inocula were verified not to directly inhibit the mycelial growth of B. cinerea based on in vitro culture plate assays. Additionally, real‐time RT‐PCR analysis verified that the active ingredient increased the expression levels of defence‐related genes, such as PR‐1(P6) and P4, in the leaves of tomato seedlings. These results suggest that the active ingredient has the potential to suppress gray mold disease in tomato, not through direct antagonistic interactions with B. cinerea, but rather through systemic activation of the plant defence system by increased expression of several defence‐related genes.     

Developmental anatomy of cotyledons and leaves in has mutant of Arabidopsis thaliana

Summary. In this work, we analyzed the developmental anatomy of cotyledons and leaves in the has mutant of Arabidopsis thaliana. It is a recessive T-DNA insertion mutation that causes changes in the size, shape, and tissue organization of the cotyledons and leaves of has plants. Analysis of has cotyledons revealed a prominent decrease in the cell number and an increase in the area of cotyledon cells and intercellular spaces of has plants. At early stages of development, has leaves are fingerlike structures, but later they develop small, lobed blades with rare trichomes. An important characteristic of the mutant leaf anatomy is the absence of mesophyll tissue differentiation. In addition, both cotyledons and leaves display a disrupted pattern of vascular bundles. Furthermore, mutant plants are defective in root and shoot morphology, indicating that the has mutation affects a number of aspects in plant development. Correspondence and reprints: Institute of Botany and “Jevremovac” Botanical Garden, Faculty of Biology, Belgrade University, Takovska 43, 11 000 Belgrade, Serbia.     

Relationship between gibberellin and cytokinin activity and flowering in Rosa damascena Mill.

Kinetin at 10 mg l^–1 increased the number of flowers produced on Rosa damascena plants while GA₃ inhibited flowering. In the leaves of non-flowering plants GA-like activity was high while specific cytokinin activity (fraction-II) was significantly higher in flowering plants. A novel compound 10- methyldihydrozeatin riboside and isopentenyl-adenine were identified from TLC fraction-II while TLC fraction-I yielded zeatin and 2-hydroxy-6-methylaminopurine.Abbreviations TLC thin layer chromatography - BA N⁶-benzyladenine - GA₃ gibberellic acid CIMAP communication No. 92-40J     

Genome-wide identification and expression analysis of extensin genes in tomato

Extensins (EXTs) are major protein components in plant cell walls that play crucial roles in higher plants. The function of EXTs has been reported in several plants but is limited in tomato, especially in fruit ripening. In this study, we identified 83 EXTs in tomato, and divided them into seven groups. The gene intron-exon structure and protein-motif composition of SlEXTs were similar within each group but different among groups. SlEXT genes showed different expression patterns in roots, leaves, flowers and fruits, and some SlEXT gene expressions in flowers could be regulated by treatments of auxin, gibberellic acid and jasmonic acid. In particular, SlSEXT8 had higher and increased expression during tomato fruit ripening, and its expression could be induced by ethylene, suggesting SlSEXT8 may be involved in tomato fruit softening. The result provides insights into the function of EXTs, and will facilitate to further study EXT roles in tomato fruit ripening.     

Gibberellic Acid Reduces Flowering Intensity in Sweet Orange [Citrus sinensis (L.) Osbeck] by Repressing CiFT Gene Expression

In Citrus, gibberellic acid (GA₃) applied at the floral bud inductive period significantly reduces flowering intensity. This effect is being used to improve the fruit set of parthenocarpic cultivars that tend to flower profusely. However, the molecular mechanisms involved in the process remain unclear. To contribute to the knowledge of this phenomenon, adult trees of ‘Salustiana’ sweet orange were sprayed at the floral bud inductive period with 40?mg?L^?1 of GA₃ and the expression pattern of flowering genes was examined up to the onset of bud sprouting. Trees sprayed with paclobutrazol (PBZ, 2,000?mg L^?1), a gibberellin biosynthesis inhibitor, were used to confirm the effects, and untreated trees served as control. Bud sprouting, flowering intensity, and developed shoots were evaluated in the spring. GA₃ significantly reduced the number of flowers per 100 nodes by 72% compared to the control, whereas PBZ increased the number by 123%. Data of the expression pattern of flowering genes in leaves of GA₃-treated trees revealed that this plant growth regulator inhibited flowering by repressing relative expression of the homolog of FLOWERING LOCUS T, CiFT, whereas PBZ increased flowering by boosting its expression. The activity of the homologs TERMINAL FLOWER 1, FLOWERING LOCUS C, SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1, and APETALA1 was not affected by the treatments. The number of flowers per inflorescence, in both leafy and leafless inflorescences, was not altered by GA₃ but increased with PBZ; the latter paralleled LEAFY relative expression. These results suggest that GA₃ inhibits flowering in Citrus by repressing CiFT expression in leaves.     

Expressing the yeast HAL1 gene in tomato increases fruit yield and enhances K+/Na+ selectivity under salt stress

The yeast HAL1 gene facilitates K⁺/Na⁺ selectivity and salt tolerance of cells. Ectopic expression of HAL1 in transgenic tomato (Lycopersicon esculentum Mill.) plants minimized the reduction in fruit production caused by salt stress. Maintenance of fruit production by transgenic plants was correlated with enhanced growth under salt stress of calli derived from the plants. The HAL1 transgene enhanced water and K⁺ contents in both leaf calli and leaves in the presence of salt, which indicates that HAL1 functions in plants using a similar mechanism to that in yeast, namely by facilitating K⁺/Na⁺ selectivity under salt stress.     

Stamenless, a tomato mutant with homeotic conversions in petals and stamens

A tomato (Lycopersicon esculentum Mill.) monogenic semidominant mutation, stamenless (sl), which results in homeotic conversions in two adjacent floral whorls, was studied. When grown at standard temperature, flowers of sl/sl plants showed sepaloid petals in the second whorl and strong transformation of stamens to carpels in whorl three. These transformed carpels were fused with each other and with the genuine carpels in the fourth whorl to form a unique gynoecium. The mutation is semidominant since heterozygous plants showed a phenotype intermediate between that of the wild type (WT) and that of homozygous mutant plants, with nearly WT petals but with feminized stamens bearing naked ovules on the base of their adaxial face. The initiation and position of organ primordia in sl/sl flowers were not altered when compared with WT primordia although development of organ primordia in the second and third whorls deviated from WT at an early stage as observed by scanning electron microscopy. The mutant phenotype is temperature sensitive and when sl/sl plants were cultured at low temperature, the morphology of some flowers resembled that of the WT. This reversion of the mutant phenotype is also induced by treatment of young sl/sl plants with gibberellic acid, providing evidence that gibberellin synthesis or sensitivity could mediate the effect of low temperature on the mutant phenotype. Southern blot analyses using a Deficiens-homologous gene from Solanum tuberosum as a probe showed a restriction-fragment-length polymorphism (RFLP) linked to the sl mutation. This result indicates that the mutation affects a Deficiens-like gene that controls the identity of petals and stamens. Received: 10 December 1998 / Accepted: 29 March 1999