Houcheng Liu

Phosphorus Deficiency Restricts Plant Growth but Induces Pigment Formation in the Flower Stalk of Chinese Kale

The effect of phosphorus (P) nutrition on plant growth and pigment formation in the flower stalk was studied under hydroponic conditions for 2 Chinese kale (Brassica alboglabra Bailey) cultivars: ‘Jianyexia’ (green flower stalk) and ‘Hongjiao’ (mauve flower stalk). Three different P treatments were used: 30 (normal-P), 7.5 (low-P), and 0 mg·L−1 (P-deficient). The results showed that the biomass, yield, plant height, stem diameter, and leaf number of Chinese kale were significantly reduced in the low-P and P-deficient treatments compared to the normal-P treatment. The chlorophyll content in the flower stalk epidermis was not affected by different P levels in ‘Jianyexia’, but was significantly reduced by the P-deficient treatment in ‘Hongjiao’. Decreased P levels caused the flavonoid, soluble phenol, and anthocyanin content of the flower stalks to gradually increase in both Chinese kale cultivars. The pH value of the flower stalk epidermis gradually decreased with the declining P levels, and was significantly different among the 3 treatments. As the P levels declined, phenylalanine ammonia-lyase (PAL) and chalcone isomerase (CHI) activities in the flower stalk epidermis gradually increased, and were significantly different among the 3 treatments. P nutrition may control the synthesis of anthocyanins in the flower stalk by regulating the epidermal pH value, and the activities of PAL and CHI.

Cloning and characterization of the ammonium transporter genes BaAMT1;1 and BaAMT1;3 from Chinese kale

Chinese kale (Brassica alboglabra L.) is a popular vegetable rich in important nutrients. Fertilization with appropriate ammonium:nitrate ratios enhances biomass production and quality. AMT-type ammonium transporters have been shown to mediate ammonium uptake across the plasma membrane. However, very little is known about the molecular regulation of growth and development by ammonium in Chinese kale, including how ammonium regulates the expression of AMT1 genes. In this study, we identified and characterized two AMT1 genes from B. alboglabra, BaAMT1;1 and BaAMT1;3. The full-length open reading frames of BaAMT1;1 and BaAMT1;3 were 1512 bp and 1515 bp, respectively. Transient expression of the fusion proteins pBE-EGFP-BaAMT1;1 and pBE-EGFP-BaAMT1;3 in onion epidermal cells indicated that these transporters are located on the plasma membrane. BaAMT1;1 and BaAMT1;3 were functional in yeast and complemented a mutant defective in ammonium transport. BaAMT1;1 was expressed in vegetative organs and at high levels in roots, while BaAMT1;3 expression was root specific. In addition, we observed opposite responses of BaAMT1;1 and BaAMT1;3 expression to nitrogen starvation and ammonium resupply in roots. These results provide new insights into the molecular mechanisms underlying ammonium absorption in Chinese kale.

Uptake Kinetics of Different Nitrogen Forms by Chinese Kale

ABSTRACT In this paper, the uptake kinetics of various nitrogens (nitrate (NO3−), ammonium (NH4+), urea, amino acid) by Chinese kale (Brassica oleracea L. var. Bailey) were studied under hydroponic condition. The results indicated that the uptake kinetics of organic and inorganic nitrogen (N) by Chinese kale conform to the Michaelis–Menten equation, and the maximum uptake rate (Vmax) and affinity index (1/Km) showed nitrate (NO3—N) > ammonium (NH4+-N) > urea-N > Gly-N, with significant differences between treatments (p < 0.05). Adding different types of N to NO3− nutrient solution had little impact on its affinity, but significantly decreased the NO3− Vmax, which showed NO3–N > NO3− + NH4+ > NO3− + urea > NO3− + Gly. Chinese kale preferred inorganic N to organic N, with NO3− preceding NH4+. Adding organic and NH4+ N to nutrient solution reduced the NO3− uptake capacity by the plant.

Effect of Ammonium and Nitrate Ratios on Growth and Yield of Flowering Chinese Cabbage

The effect of different ammonium and nitrate ratios (NH4 + -N : NO3 −-N = 0:100, 25:75, 50:50 and 75:25) on growth and yield of flowering Chinese cabbage (Brassica campestris L. ssp. chinensis var. utilis Tsen et Lee) with 3 cultivars were studied in hydroponics. The results indicated that, compared with the complete nitrate treatment, plant height, stem diameter and biomass of flowering Chinese cabbage were increased in the low enhancement of ammonium (25%) in nutrient solution, while plant growth and biomass were decreased in the medium (50%) and high (75%) enhancement of ammonium. Compared with the complete nitrate treatment, low enhancement of ammonium (25%) in nutrient solution increased root activity of flowering Chinese cabbage, while it was decreased by the medium (50%) and high (75%) enhancement of ammonium treatments. Nutrient solution with 25% ammonium enhancement maintained a high root absorption capacity and increased plant biomass, so it was appropriate to hydroponics for flowering Chinese cabbage.

Genome-wide identification, phylogeny analysis, expression profiling, and determination of protein-protein interactions of the LEUNIG gene family members in tomato

Members of the LEUNIG gene family have recently emerged as key players in gene repression, affecting several developmental mechanisms in plants, especially flower development. LEUNIG proteins function via recruiting adaptor SEUSS proteins. Nevertheless, no systematic studies on the LEUNIG and SEUSS gene families have been undertaken in tomato (Solanum lycopersicum, a fleshy fruit-bearing model plant, belonging to the Solanaceae family). Here, we present the results of a genome-wide analysis of tomato LEUNIG and SEUSS genes. In our study, we identified three SlLUG and four SlSEU genes. All three SlLUG full-length proteins contained the LEUNIG canonical domains (LUFS and two WD40 repeats), and the four full-length SlSEU genes contained the Lim-binding domain. All the members of the SlLUG and SlSEU family proteins were localized to the nucleus. All the SlSEU and SlLUG genes were detected in the tomato tissues tested. Expression analysis showed that the SlLUGs and SlSEUs exhibited tissue-specific expression, and that they responded to exogenous plant hormone and stress treatment. Protein-protein interaction analysis showed that only SlLUGs, but not SlSEUs, interacted with SlYABBY. Only a weak interaction between SlLUG1 and SlSEU3 was observed among all the SlLUG and SlSEU proteins. Taken together, these findings may help elucidate the roles played by SlLUG and SlSEU family members in plant growth and development.

Effects of partial replacement of nitrate with different nitrogen forms on the yield, quality and nitrate content of Chinese kale

ABSTRACT In this study, the yields, nutritional qualities and nitrate (NO3) content of Chinese kale were studied with two cultivars, following partial replacement of nitrate (20%) with ammonium (NH4), urea and glycine in hydroponics. The results showed that, compared with the full nitrate treatment, ammonium replacement increased the fresh weight by 18.1% and 8.0% of ‘Zaobao’ and ‘Lvbao’ cultivars respectively, whereas urea and glycine replacements decreased the biomass significantly. Adding different nitrogen (N) forms significantly improved the contents of vitamin C, soluble sugar, free amino acid, protein, soluble phenol and flavonoids in Chinese kale. Adding the three alternative N forms also reduced nitrate content significantly, in which glycine replacement was the lowest. According to the results obtained, different forms of N replacement could be used for different purposes. Glycine replacement could be the best alternative only to improve qualities, while ammonium replacement could be the best alternative to improve both the yield and qualities.

Comparative RNA-Seq analysis on the regulation of cucumber sex differentiation under different ratios of blue and red light

Cucumber (Cucumis sativus L.) is a typical monoecism vegetable with individual male and female flowers, which has been used as a plant model for sex determination. It is well known that light is one of the most important environmental stimuli, which control the timing of the transition from vegetative growth to reproductive development. However, whether light controls sex determination remains elusive. To unravel this problem, we performed high-throughput RNA-Seq analyses, which compared the transcriptomes of shoot apices between R2B1(Red light:Blue light = 2:1)-treated and R4B1(Red light:Blue light = 4:1)-treated cucumber seedlings. Results showed that the higher proportion of blue light in the R2B1 treatment significantly induced the formation of female flowers and accelerated female flowering time in this whole study. The genes related to flowering time, such as flowering locus T (FT) and SUPPRESSOR OF OVEREXPRESSION OF CO1 (SOC1), were up-regulated after R2B1 treatment. Furthermore, the transcriptome analysis showed that up-regulation and down-regulation of specific DEGs (the differentially expressed genes) were primarily the result of plant hormone signal transduction after treatments. The specific DEGs related with auxin formed the highest percentage of DEGs in the plant hormone signal transduction. In addition, the expression levels of transcription factors also changed after R2B1 treatment. Thus, sex differentiation affected by light quality might be induced by plant hormone signal transduction and transcription factors. These results provide a theoretical basis for further investigation of the regulatory mechanism of female flower formation under different light qualities in cucumber seedlings.

Transcriptomic analysis of the regulation of stalk development in flowering Chinese cabbage (Brassica campestris) by RNA sequencing

Flowering Chinese cabbage is a stalk vegetable whose quality and yield are directly related to stalk development. However, no comprehensive investigations on stalk development have been performed. To address this issue, the present study used RNA sequencing to investigate transcriptional regulation at three key stages (seedling, bolting, and flowering) of stalk development in flowering Chinese cabbage. Anatomical analysis revealed that cell division was the main mode of stalk thickening and elongation at all key stages. Among the 35,327 genes expressed in shoot apices, 34,448 were annotated and 879 were identified as novel transcripts. We identified 11,514 differentially expressed genes (DEGs) among the three stages of stalk development. Functional analysis revealed that these DEGs were significantly enriched in ‘ribosome’ and ‘plant hormone signal transduction’ pathways and were involved in hormone signal transduction, cell cycle progression, and the regulation of flowering time. The roles of these genes in stalk development were explored, and a putative gene-regulation network for the stalk flowering time was established. These findings provide insight into the molecular mechanisms of stalk development in flowering Chinese cabbage that provides a new theoretical basis for stalk vegetable breeding.

Low temperature during seedling stage promotes female flower determination but not yield of Chieh-qua

Temperature has an important effect on plant growth and sex determination in flowers. The effect of different temperatures (high temperature: 30°C /25°C (day/night), medium temperature: 25°C /18°C and low temperature: 15°C /10°C ) on flower sex determination and fruit yield was studied in Chieh-qua (Benincasa hispida Cogn. var. Chieh-qua How. ‘No. 4 Jiang xin’), also the content of absicsic acid (ABA) and indole acetic acid (IAA) in the shoot apex was measured. The results showed that medium and low temperatures during seedling stage boost the female flower differentiation after transplanting, compared with high temperature treatment, and the effect was more obvious when the temperature was lower. Lower temperature increased the content of ABA and IAA in shoot apex of Chieh-qua. There was a positive relationship between the ratio of IAA/ABA and plant female flower determination under different temperature treatments (R2 = 0.8744). Temperature may affect female flower differentiation of Chieh-qua by changing the contents of ABA and IAA in shoot apex. Fruit yield was not significantly affected by different temperature treatments.