Expression and regulation of theRSI-1 gene during lateral root initiation

The tomato geneRSI-1 was previously identified as a molecular marker for auxin-induced lateral root initiation. We have further characterized the expression mode of theRSI-1 gene in tomato andArabidopsis thaliana. Northern blot analyses revealed that the gene was induced specifically by auxin in tomato roots and hypocotyls. For experiments with transgenic plants, the 5′ flanking region of theRSI-1 gene was linked to a GUS reporter gene, then transformed into tomato andArabidopsis. In these transgenic tomato plants, GUS activity was detected at the sites of initiation for lateral and adventitious roots. Expression of the fusion gene was auxin-dependent and tissue-specific. This was consistent with results from the northern blot analyses. In transgenicArabidopsis, the overall expression pattern of theRSI-GUS gene, including tissue specificity and auxin inducibility, was comparable to that in transgenic tomato seedlings. These results indicate that an identical regulatory mechanism for lateral root initiation might be conserved in both plants. Thus, the expression mode of theRSI-CUS gene inArabidopsis mutants defective in lateral root development should be investigated to provide details of this process.     

Light modulates the root tip excision induced lateral root formation in tomato

During plant growth and development, root tip performs multifarious functions integrating diverse external and internal stimuli to regulate root elongation and architecture. It is believed that a signal originating from root tip inhibits lateral root formation (LRF). The excision of root tip induced LRF in tomato seedlings associated with accumulation of auxin in pericycle founder cells. The excision of cotyledons slightly reduced LRF, whereas severing shoot from root completely abolished LRF. Exogenous ethylene application did not alter LRF. The response was modulated by light with higher LRF in seedlings exposed to light. Our results indicate that light plays a role in LRF in seedlings by likely modulating shoot derived auxin.     

Mutations in the Diageotropica (Dgt) gene uncouple patterned cell division during lateral root initiation from proliferative cell division in the pericycle

In angiosperms, root branching requires a continuous re-initiation of new root meristems. Through some unknown mechanism, in most eudicots pericycle cells positioned against the protoxylem change identity and initiate patterned division, leading to formation of lateral root primordia that further develop into lateral roots. This process is auxin-regulated. We have observed that three mutations in the Diageotropica (Dgt) gene in tomato prevent primordium formation. Detailed analysis of one of these mutants, dgt1-1, demonstrated that the mutation does not abolish the proliferative capacity of the xylem-adjacent pericycle in the differentiated root portion. Files of shortened pericycle cells found in dgt1-1 roots were unrelated to primordium formation. Auxin application stimulated this unusual proliferation, leading to formation of a multi-layered xylem-adjacent pericycle, but did not rescue the primordium formation. In contrast to wild type, auxin could not induce any cell divisions in the pericycle of the most distal dgt1-1 root-tip portion. In wild-type roots, the Dgt gene promoter was expressed strongly in lateral root primordia starting from their initiation, and on auxin treatment was induced in the primary root meristem. Auxin level and distribution were altered in dgt1-1 root tissues, as judged by direct auxin measurements, and the tissue-specific expression of an auxin-response reporter was altered in transgenic plants. Together, our data demonstrate that the Dgt gene product, a type-A cyclophilin, is essential for morphogenesis of lateral root primordia, and that the dgt mutations uncouple patterned cell division in lateral root initiation from proliferative cell division in the pericycle.     

Plant-derived smoke solutions stimulate the growth of Lycopersicon esculentum roots in vitro

Aqueous extracts of smoke, derived from Themeda triandra, a fire-climax grass, and Passerina vulgaris, a fynbos plant, stimulated the growth of primary root sections of tomato roots in suspension culture. The optimal dilution for both extracts was 1:2000. Several of the fractions obtained from TLC separation of the Themeda and the Passerina extracts significantly promoted primary root growth. The auxins naphthaleneacetic acid (NAA), indolebutyric acid (IBA) and indoleacetic acid (IAA) were found to stimulate the growth of the primary root axis, with IAA and NAA significantly promoting lateral root number. Similarly, the naturally occurring cytokinins, zeatin and its derivatives (zeatin-O-glucoside; dihydrozeatin and zeatin riboside) stimulated primary root length. Zeatin and dihydrozeatin promoted secondary root growth, but only at very low concentrations.     

Expression of cysteine sulfinate decarboxylase (CSD) in male reproductive organs of mice

Cysteine sulfinate decarboxylase (CSD) is the rate-limiting biosynthetic enzyme of taurine, but it is still controversial whether the male reproductive organs have the function to synthesize taurine through CSD pathway. The present study was thus undertaken to detect CSD expression in male mouse reproductive organs by RT-PCR, Western blot and immunohistochemistry. The results show that CSD is expressed both at the mRNA and protein levels in the testis, epididymis and ductus deferens. The relative levels of both CSD mRNA and protein increase from the testis to the epididymis and to the ductus deferens. Immunohistochemical results demonstrate that the main cell types containing CSD are Leydig cells of testis, epithelial cells and some stromal cells throughout the efferent ducts, epididymis and ductus deferens. These results suggest that male genital organs have the function to produce taurine through the CSD pathway, although quantifying the relation of CSD expression to taurine synthesis and the exact functions of taurine in male genital organs still need to be elucidated in future studies.     

泽兰实蝇内生殖器官的结构及其发育状况

【背景】泽兰实蝇属双翅目实蝇科,是杂草紫茎泽兰的重要专性天敌。该蝇幼虫可蛀入紫茎泽兰内部形成虫瘿,有效控制紫茎泽兰的扩散,许多国家都利用泽兰实蝇控制紫茎泽兰的危害。【方法】通过光学显微法观察了泽兰实蝇成虫内生殖器官的结构及其发育动态。【结果】雌性泽兰实蝇的内生殖系统主要由卵巢、输卵管、受精囊、雌性附腺等器官组成,雄性生殖系统由精巢、输精管、雄性附腺、射精管组成。在成虫发育过程中,雌虫卵巢的长度在第4日龄时达最大值,宽度在1日龄时达最大值,与其他日龄相比有显著差异,雌性附腺及受精囊的大小在各日龄间无显著差异;雄虫精巢长度在4日龄时达到最大,宽度在2日龄时达最大,且不同日龄间也有显著差异,而雄性附腺的大小在不同龄期间无显著差异。【结论与意义】本文阐明了泽兰实蝇的内生殖系统结构与发育状况,这有助于为提高泽兰实蝇人工繁殖效率及生物防治效果奠定理论基础。     

Association of vegetative and reproductive organs of platanoids (Angiospermae): significance for systematics and phylogeny

Some examples of association between platanoid leaves and various reproductive structures are considered. The expediency of determining dispersed Cretaceous platanoid leaves using a morphological system that is independent of the system of modern plants is discussed. It is confirmed that leaf structures are more conservative than reproductive organs. It is proposed that, in the geological past, there was a polymorphic group that was probably represented by extinct families which gave rise to modern families (in particular, Platanaceae and Hamamelidaceae).     

Potassium carrier TRH1 is required for auxin transport in Arabidopsis roots

Disruption of the TRH1 potassium transporter impairs root hair development in Arabidopsis, and also affects root gravitropic behaviour. Rescue of these morphological defects by exogenous auxin indicates a link between TRH1 activity and auxin transport. In agreement with this hypothesis, the rate of auxin translocation from shoots to roots and efflux of [3H]IAA in isolated root segments were reduced in the trh1 mutant, but efflux of radiolabelled auxin was accelerated in yeast cells transformed with the TRH1 gene. In roots, Pro(TRH1):GUS expression was localized to the root cap cells which are known to be the sites of gravity perception and are central for the redistribution of auxin fluxes. Consistent with these findings, auxin-dependent DR5:GUS promoter-reporter construct was misexpressed in the trh1 mutant indicating that partial block of auxin transport through the root cap is associated with upstream accumulation of the phytohormone in protoxylem cells. When [K+] in the medium was reduced from 20 to 0.1 mm, wild type roots showed mild agravitropic phenotype and DR5:GUS misexpression in stelar cells. This pattern of response to low external [K+] was also affected by trh1 mutation. We conclude that the TRH1 carrier is an important part of auxin transport system in Arabidopsis roots.     

巨龙竹生殖器官形态结构及雌、雄配子体的发育

通过石蜡切片的方法对巨龙竹生殖器官结构、大小孢子的发生和雌、雄配子体的发育过程进行了观察研究。 巨龙竹为一心皮组成的单室单子房,子房内具有一个胚珠,倒生、双珠被、厚珠心。大孢子母细胞减数分裂形成线形排列的4个大孢子,合点端大孢子具功能。胚囊的发育为蓼型,具多个反足细胞。巨龙竹的花药壁由4层结构组成,包括表皮、药室内壁、中层、绒毡层;花药壁发育为单子叶型,绒毡层为腺质型。小孢子母细胞减数分裂中的胞质分裂为连续型,四分孢子为四面体型;成熟花粉粒为2细胞型,具1个萌发孔。小穗发育雌雄异熟,雌蕊的发育早于雄蕊的发育。     

Morphology of the female reproductive organs of the African lion (Panthera leo)

The topography and splanchnology of the reproductive organs of the African lioness were studied and described in situ and after removal. The kidneys were located far caudally in relation to the thirteenth ribs. The suspensory ligament was very well developed, originated in a fan‐like manner from the dorsolateral abdominal wall lateral to the kidney and extended up to a few centimetres cranial to the kidney. The proper ligament of the ovary as well as the round ligament was well developed. The round ligament inserted on the medial femoral fascia. The left ovary was bigger than the right. The ovarian bursa had a short mesosalpinx that did not cover any part of the ovary and the fimbriae extended along the entire length. The urethral tuberculum as well as the urethral crest were well developed. The left uterine horn was longer than the right. The uterine tube was found to open directly into the tip of the uterine horn and not onto a papilla. The reproductive organs of the lioness resembled those of the domestic cat and dog but with some major differences.     

Conservation and divergence of signalling pathways between roots and soil microbes – the Rhizobium-legume symbiosis compared to the development of lateral roots, mycorrhizal interactions and nematode-induced galls

This review compares endophytic symbiotic and pathogenic root–microbe interactions and examines how the development of root structures elicited by various micro-organisms could have evolved by recruitment of existing plant developmental pathways. Plants are exposed to a multitude of soil micro-organisms which affect root development and performance. Their interactions can be of symbiotic and pathogenic nature, both of which can result in the formation of new root structures – how does the plant regulate the different outcomes of interactions with microbes? The idea that pathways activated in plant by micro-organisms could have been `hijacked' from plant developmental pathways is not new, it was essentially proposed by P. S. Nutman in 1948, but at that time, the molecular evidence to support that hypothesis was missing. Genetic evidence for overlaps between different plant–microbe interactions have previously been examined. This review compares the physiological and molecular plant responses to symbiotic rhizobia with those to arbuscular mycorrhizal fungi, pathogenic nematodes and the development of lateral roots and summarises evidence from both molecular and cellular studies for substantial overlaps in the signalling pathways underlying root–micro-organism interactions. A more difficult question has been why plant responses to micro-organisms are so similar, even though the outcomes are very different. Possible hypotheses for divergence of signalling pathways and future approaches to test these ideas are presented.     

Auxin signaling modulates LATERAL ROOT PRIMORDIUM1 (LRP1) expression during lateral root development in Arabidopsis

Auxin signaling mediated by various auxin/indole‐3‐acetic acid (Aux/IAAs) and AUXIN RESPONSE FACTORs (ARFs) regulate lateral root (LR) development by controlling the expression of downstream genes. LATERAL ROOT PRIMORDIUM1 (LRP1), a member of the SHORT INTERNODES/STYLISH (SHI/STY) family, was identified as an auxin‐inducible gene. The precise developmental role and molecular regulation of LRP1 in root development remain to be understood. Here we show that LRP1 is expressed in all stages of LR development, besides the primary root. The expression of LRP1 is regulated by histone deacetylation in an auxin‐dependent manner. Our genetic interaction studies showed that LRP1 acts downstream of auxin responsive Aux/IAAs‐ARFs modules during LR development. We showed that auxin‐mediated induction of LRP1 is lost in emerging LRs of slr‐1 and arf7arf19 mutants roots. NPA treatment studies showed that LRP1 acts after LR founder cell specification and asymmetric division during LR development. Overexpression of LRP1 (LRP1 OE) showed an increased number of LR primordia (LRP) at stages I, IV and V, resulting in reduced emerged LR density, which suggests that it is involved in LRP development. Interestingly, LRP1‐induced expression of YUC4, which is involved in auxin biosynthesis, contributes to the increased accumulation of endogenous auxin in LRP1 OE roots. LRP1 interacts with SHI, STY1, SRS3, SRS6 and SRS7 proteins of the SHI/STY family, indicating their possible redundant role during root development. Our results suggested that auxin and histone deacetylation affect LRP1 expression and it acts downstream of LR forming auxin response modules to negatively regulate LRP development by modulating auxin homeostasis in Arabidopsis thaliana.     

Overexpression of tomato LeAGP-1 arabinogalactan-protein promotes lateral branching and hampers reproductive development

LeAGP-1 is a glycosylphosphatidylinositol (GPI)-anchored arabinogalactan-protein (AGP) in tomato (Lycopersicon esculentum). Patterns of mRNA expression and protein localization for LeAGP-1 indicate that it likely functions in certain aspects of plant growth and development. To elucidate LeAGP-1 function(s), transgenic tomato plants expressing enhanced green fluorescent protein (GFP) fused to LeAGP-1 [GFP-LeAGP-1] or two LeAGP-1 variants, one lacking the C-terminal GPI-anchor domain [GFP-LeAGP-1DeltaC] and the other lacking the lysine-rich domain [GFP-LeAGP-1DeltaK], under the control of the CaMV35S promoter were produced using Agrobacterium-mediated transformation. Transgenic T0 and T1 lines with high levels of both GFP-LeAGP-1 mRNA and protein: (i) were significantly shorter; (ii) were highly branched; (iii) produced more flower buds, but most of these flowers did not mature, resulting in less fruit production; and (iv) produced seeds that were significantly smaller than normal seeds. Overexpression of LeAGP-1DeltaK had a similar or even more pronounced effect on plant vegetative and reproductive growth, while the effect of LeAGP-1DeltaC overexpression on plant reproduction was minimal. These results indicate that the GPI anchor is critical for LeAGP-1 function. As the phenotype of GFP-LeAGP-1 overexpressing transgenic plants is similar to that of cytokinin-overproducing plants, mRNA expression patterns of LeAGP-1 under different hormone treatments were examined. Cytokinins upregulated LeAGP-1 mRNA expression, while auxins and ABA inhibited LeAGP-1 mRNA expression. Based on these results, GPI-anchored LeAGP-1 most likely functions in plant growth and development in concert with auxin/cytokinin signaling.     

Asymmetric cytokinin signaling opposes gravitropism in roots

Plants depend on gravity to provide the constant landmark for downward root growth and upward shoot growth. The phytohormone auxin and its cell‐to‐cell transport machinery are central determinants ensuring gravitropic growth. Statolith sedimentation toward gravity is sensed in specialized cells. This positional cue is translated into the polar distribution of PIN auxin efflux carriers at the plasma membrane, leading to asymmetric auxin distribution and consequently, differential growth and organ bending. While we have started to understand the general principles of how primary organs execute gravitropism, we currently lack basic understanding of how lateral plant organs can defy gravitropic responses. Here we briefly review the establishment of the oblique gravitropic set point angle in lateral roots and particularly discuss the emerging role of asymmetric cytokinin signaling as a central anti‐gravitropic signal. Differential cytokinin signaling is co‐opted in gravitropic lateral and hydrotropic primary roots to counterbalance gravitropic root growth.     

High levels of ripening-specific reporter gene expression directed by tomato fruit polygalacturonase gene-flanking regions

The 1.4 kb 5 polygalacturonase (PG) gene-flanking region has previously been demonstrated to direct ripening-specific chloramphenicol acetyl transferase (CAT) expression in transgenic tomato plants. The steady state level of CAT mRNA in these plants was estimated to be less than 1% of the endogenous PG mRNA. Further constructs containing larger PG gene-flanking regions were generated and tested for their ability to direct higher levels of reporter gene expression. A 4.8 kb 5-flanking region greatly increased levels of ripening-specific reporter gene activity, while a 1.8 kb 3 region was only shown to have a positive regulatory role in the presence of the extended 5 region. Transgenic plants containing the CAT gene flanked by both of these regions showed the same temporal pattern of accumulation of CAT and PG mRNA, and steady-state levels of the transgene mRNA were equivalent to 60% of the endogenous PG mRNA on a per gene basis. The proximal 150 bp of the PG promoter gave no detectable CAT activity. However, the distal 3.4 kb of the 4.8 kb 5 PG promoter was shown to confer high levels of ripening-specific gene expression when placed in either orientation upstream of the 150 bp minimal promoter. The DNA sequence of the 3.4 kb region revealed a 400 bp imperfect reverse repeat, and sequences which showed similarity to functionally significant sequences from the ripening-related, ethylene-regulated tomato E8 and E4 gene promoters. The possible roles of the flanking regions in regulating PG gene expression are discussed.