The role of diaphragm as a natural resistance to the necrosis produced by pruning cuts

Long before the scientific method was created, vine pruning was established as an art as early as at the beginning of the Christian era. Pruning is a way of reducing the vegetative part of the vine in order to limit its natural growth, and thus improve yield and grape quality by controlling the number of latent buds that are left per vine. Today, Virgilio and Plineo instructions are still being followed for pruning, with the exception of some small empirical changes, which were introduced in the 19th century by Jules Guyot. This report aims to evaluate the effect of pruning cuts on wood necrosis behaviour, and to determine the effect of pruning on shoot development on different vine varieties.

Carotenoid Cleavage Dioxygenase Genes of Chimonanthus praecox, CpCCD7 and CpCCD8, Regulate Shoot Branching in Arabidopsis

Strigolactones (SLs) regulate plant shoot development by inhibiting axillary bud growth and branching. However, the role of SLs in wintersweet (Chimonanthus praecox) shoot branching remains unknown. Here, we identified and isolated two wintersweet genes, CCD7 and CCD8, involved in the SL biosynthetic pathway. Quantitative real-time PCR revealed that CpCCD7 and CpCCD8 were down-regulated in wintersweet during branching. When new shoots were formed, expression levels of CpCCD7 and CpCCD8 were almost the same as the control (un-decapitation). CpCCD7 was expressed in all tissues, with the highest expression in shoot tips and roots, while CpCCD8 showed the highest expression in roots. Both CpCCD7 and CpCCD8 localized to chloroplasts in Arabidopsis. CpCCD7 and CpCCD8 overexpression restored the phenotypes of branching mutant max3-9 and max4-1, respectively. CpCCD7 overexpression reduced the rosette branch number, whereas CpCCD8 overexpression lines showed no phenotypic differences compared with wild-type plants. Additionally, the expression of AtBRC1 was significantly up-regulated in transgenic lines, indicating that two CpCCD genes functioned similarly to the homologous genes of the Arabidopsis. Overall, our study demonstrates that CpCCD7 and CpCCD8 exhibit conserved functions in the CCD pathway, which controls shoot development in wintersweet. This research provides a molecular and theoretical basis for further understanding branch development in wintersweet.

Carotenoid Cleavage Dioxygenase Genes of Chimonanthus praecox, CpCCD7 and CpCCD8, Regulate Shoot Branching in Arabidopsis

Strigolactones (SLs) regulate plant shoot development by inhibiting axillary bud growth and branching. However, the role of SLs in wintersweet (Chimonanthus praecox) shoot branching remains unknown. Here, we identified and isolated two wintersweet genes, CCD7 and CCD8, in-volved in the SL biosynthetic pathway. Quantitative real-time PCR revealed that CpCCD7 and CpCCD8 were down-regulated in wintersweet during branching. When new shoots were formed, expression levels of CpCCD7 and CpCCD8 were almost the same as the control (un-decapitation). CpCCD7 was expressed in all tissues, with the highest expression in shoot tips and roots, while CpCCD8 showed the highest expression in roots. Both CpCCD7 and CpCCD8 localized to chloroplasts in Arabidopsis. CpCCD7 and CpCCD8 overexpression restored the phenotypes of branching mutant max3-9 and max4-1, respectively. CpCCD7 overexpression reduced the rosette branch number, whereas CpCCD8 overexpression lines showed no phenotypic differences compared with wild-type plants. Additionally, the expression of AtBRC1 was significantly up-regulated in transgenic lines, indicating that two CpCCD genes functioned similarly to the homologous genes of the Arabidopsis. Overall, our study demonstrates that CpCCD7 and CpCCD8 exhibit conserved functions in the CCD pathway, which controls shoot development in wintersweet. This research provides a molecular and theoretical basis for further understanding branch development in wintersweet.

TOR kinase controls shoot development by translational regulation of cytokinin catabolic enzymes

Plants continuously adjust the rate at which new organs are produced in accordance with endogenous and environmental signals. Therefore, a multitude of signaling pathways converge to modulate stem cell activity. We have shown previously, that the TOR kinase network integrates metabolic- and light signals to control expression of WUSCHEL, a transcriptional master regulator of stem cells in the shoot apical meristem (SAM). However, the link between TOR and WUS promoter activity remained unresolved. Here we demonstrate that TOR controls trans-Zeatin abundance, the cytokinin derivative that is the main driver of shoot development. Moreover, we identify TOR mediated translational control of cytokinin degrading CYTOKININ OXIDASES/DEHYDROGENASE (CKX) enzymes as the underlying mechanism, which allows the plant to adjust the stem cell signaling environment and growth pattern within minutes after changes in environmental parameters.

Nitric Oxide Alters the Pattern of Auxin Maxima and PIN-FORMED1 During Shoot Development

Hormone patterns tailor cell fate decisions during plant organ formation. Among them, auxins and cytokinins are critical phytohormones during early development. Nitric oxide (NO) modulates root architecture by the control of auxin spatial patterns. However, NO involvement during the coordination of shoot organogenesis remains unclear. Here, we explore the effect of NO during shoot development by using a phenotypic, cellular, and genetic analysis in Arabidopsis thaliana and get new insights into the characterization of NO-mediated leaf-related phenotypes. NO homeostasis mutants are impaired in several shoot architectural parameters, including phyllotactic patterns, inflorescence stem elongation, silique production, leaf number, and margin. Auxin distribution is a key feature for tissue differentiation and need to be controlled at different levels (i.e., synthesis, transport, and degradation mechanisms). The phenotypes resulting from the introduction of the cue1 mutation in the axr1 auxin resistant and pin1 backgrounds exacerbate the relationship between NO and auxins. Using the auxin reporter DR5:GUS, we observed an increase in auxin maxima under NO-deficient mutant backgrounds and NO scavenging, pointing to NO-ASSOCIATED 1 (NOA1) as the main player related to NO production in this process. Furthermore, polar auxin transport is mainly regulated by PIN-FORMED 1 (PIN1), which controls the flow along leaf margin and venations. Analysis of PIN1 protein levels shows that NO controls its accumulation during leaf development, impacting the auxin mediated mechanism of leaf building. With these findings, we also provide evidence for the NO opposite effects to determine root and shoot architecture, in terms of PIN1 accumulation under NO overproduction.

Growth Evaluation of In-Vitro Propagated Embryo of Morinda Citrifolia L. Seeds

The dormant nature of Morinda citrifolia seeds is a limitation to its efficient in-vitro plantlet multiplication. Hence, the use of embryo culture for successful in-vitro culture initiation. Matured embryo of freshly collected noni seeds were cultured on Murashige and Skoog basal medium supplemented with kinetin (Kn) and Benzyl amino purine (BAP) in the range of A: control (no addition); B: 0.5 mg/l Kn+1.0 mg/l BAP; C: 1.0 mg/l Kn+2.0 mg/l Bap; D: 1.5 mg/l Kn+3.0 mg/l BAP and E: 2.0 mg/l Kn+4.0 mg/l BAP. The results at 4 weeks after inoculation (WAI) showed that germination was faster from medium A without hormone whereas highest percentage germination was obtained from both medium D and E with 80 %. Medium B and C had 65 % each while medium A gave the least (40%). The development of the plantlets showed that longest shoot (3.9 cm) from medium A was closely related to 3.58 cm from Medium B while root lengths (2.28 cm) and number of adventitious roots (26) from medium A were significantly higher than other media at 12 WAI. Highest number of nodes (2.25) obtained from medium D was comparable to Media C and B while medium A had the least at 12 WAI. Number of leaves obtained was similar between the media at 12 WAI. These results indicated that using embryo is reliable for fast in-vitro propagation and shoot development of noni plant with optimum cytokinins (0.5/1.0 mg/l Kn/BAP) application. Keywords: Culture initiation, Cytokinins, Embryo culture, Plantlet, Shoot development

Case study of a rhizosphere microbiome assay on a bamboo rhizome with excessive shoots

Young Moso bamboo shoots are a very popular seasonal food. Bamboo is an important source of income for farmers and the value for cultivation has recently been estimated to $30,000 per hectare. A rare and valuable phenomenon has recently appeared where dozens of adjacent buds within a single Moso bamboo rhizome have grown into shoots. Due to its rarity, this phenomenon, which is of practical importance for the production of edible shoots, has not been scientifically studied. We report the occurrence of a rhizome with 18 shoots, of which the microbiome were analyzed, using rhizomes having one or no shoots as controls. The community of prokaryotes, but not fungi, correlated with the shoot numbers. Burkholderia was the most abundant genus, which negatively correlated with rhizome shoot number, while Clostridia and Ktedonobacteria positively correlated with many shoots. Two Burkholderia strains were isolated and their plant-growth promoting activity was tested. The isolated Burkholderia strains attenuated the growth of bamboo seedlings. Analysis of collected events of enhanced shoot production in China showed no evidence that enhanced shoot development was heritable. Overall, our data provides a firsthand study on excessive shoot development of bamboo.

The Cytokinin Status of the Epidermis Regulates Aspects of Vegetative and Reproductive Development in Arabidopsis thaliana

The epidermal cell layer of plants has important functions in regulating plant growth and development. We have studied the impact of an altered epidermal cytokinin metabolism on Arabidopsis shoot development. Increased epidermal cytokinin synthesis or breakdown was achieved through expression of the cytokinin synthesis gene LOG4 and the cytokinin-degrading CKX1 gene, respectively, under the control of the epidermis-specific AtML1 promoter. During vegetative growth, increased epidermal cytokinin production caused an increased size of the shoot apical meristem and promoted earlier flowering. Leaves became larger and the shoots showed an earlier juvenile-to-adult transition. An increased cytokinin breakdown had the opposite effect on these phenotypic traits indicating that epidermal cytokinin metabolism can be a factor regulating these aspects of shoot development. The phenotypic consequences of abbreviated cytokinin signaling in the epidermis achieved through expression of the ARR1-SRDX repressor were generally milder or even absent indicating that the epidermal cytokinin acts, at least in part, cell non-autonomously. Enhanced epidermal cytokinin synthesis delayed cell differentiation during leaf development leading to an increased cell proliferation and leaf growth. Genetic analysis showed that this cytokinin activity was mediated mainly by the AHK3 receptor and the transcription factor ARR1. We also demonstrate that epidermal cytokinin promotes leaf growth in a largely cell-autonomous fashion. Increased cytokinin synthesis in the outer layer of reproductive tissues and in the placenta enhanced ovule formation by the placenta and caused the formation of larger siliques. This led to a higher number of seeds in larger pods resulting in an increased seed yield per plant. Collectively, the results provide evidence that the cytokinin metabolism in the epidermis is a relevant parameter determining vegetative and reproductive plant growth and development.