Liwu Zhang

Overexpression of UDP-glucose pyrophosphorylase gene could increase cellulose content in Jute (Corchorus capsularis L.)

In this study, the full-length cDNA of the UDP-glucose pyrophosphorylase gene was isolated from jute by homologous cloning (primers were designed according to the sequence of UGPase gene of other plants) and modified RACE techniques; the cloned gene was designated CcUGPase. Using bioinformatic analysis, the gene was identified as a member of the UGPase gene family. Real-time PCR analysis revealed differential spatial and temporal expression of the CcUGPase gene, with the highest expression levels at 40 and 120d. PCR and Southern hybridization results indicate that the gene was integrated into the jute genome. Overexpression of CcUGPase gene in jute revealed increased height and cellulose content compared with control lines, although the lignin content remained unchanged. The results indicate that the jute UGPase gene participates in cellulose biosynthesis. These data provide an important basis for the application of the CcUGPase gene in the improvement of jute fiber quality.

BnaC9.SMG7b Functions as a Positive Regulator of the Number of Seeds per Silique in Brassica napus by Regulating the Formation of Functional Female Gametophytes.

A major QTL encodes a small protein with an Arabidopsis homolog and promotes the formation of functional ovules, thus yielding more seeds per silique in Brassica napus. Number of seeds per silique (NSS) is an important determinant of seed yield potential in Brassicaceae crops, and it is controlled by naturally occurring quantitative trait loci. We previously mapped a major quantitative trait locus, qSS.C9, on the C9 chromosome that controls NSS in Brassica napus. To gain a better understanding of how qSS.C9 controls NSS in B. napus, we isolated this locus through a map-based cloning strategy. qSS.C9 encodes a predicted small protein with 119 amino acids, designated as BnaC9.SMG7b, that shows homology with the Ever ShorterTelomere1 tertratricopeptide repeats and Ever Shorter Telomere central domains of Arabidopsis (Arabidopsis thaliana) SUPPRESSOR WITH MORPHOGENETIC EFFECTS ON GENITALIA7 (SMG7). BnaC9.SMG7b plays a role in regulating the formation of functional female gametophyte, thus determining the formation of functional megaspores and then mature ovules. Natural loss or artificial knockdown of BnaC9.SMG7b significantly reduces the number of functional ovules per silique and thus, results in decreased seed number, indicating that qSS.C9 is a positive regulator of NSS in B. napus. Sequence and function analyses show that BnaC9.SMG7b experiences a subfunctionalization process that causes loss of function in nonsense-mediated mRNA decay, such as in Arabidopsis SMG7. Haplotype analysis in 84 accessions showed that the favorable BnaC9.SMG7b alleles are prevalent in modern B. napus germplasms, suggesting that this locus has been a major selection target of B. napus improvement. Our results represent the first step toward unraveling the molecular mechanism that controls the natural variation of NSS in B. napus.

Genetic Structure and Relationship Analysis of an Association Population in Jute (Corchorus spp.) Evaluated by SSR Markers

Population structure and relationship analysis is of great importance in the germplasm utilization and association mapping. Jute, comprised of white jute (C. capsularis L) and dark jute (C. olitorius L), is second to cotton in its commercial significance in the world. Here, we assessed the genetic structure and relationship in a panel of 159 jute accessions from 11 countries and regions using 63 SSRs. The structure analysis divided the 159 jute accessions from white and dark jute into Co and Cc group, further into Co1, Co2, Cc1 and Cc2 subgroups. Out of Cc1 subgroup, 81 accessions were from China and the remaining 10 accessions were from India (2), Japan (5), Thailand, Vietnam (2) and Pakistan (1). Out of Cc2 subgroup, 35 accessions were from China, and the remaining 3 accessions were from India, Pakistan and Thailand respectively. It can be inferred that the genetic background of these jute accessions was not always correlative with their geographical regions. Similar results were found in Co1 and Co2 subgroups. Analysis of molecular variance revealed 81% molecular variation between groups but it was low (19%) within subgroups, which further confirmed the genetic differentiation between the two groups. The genetic relationship analysis showed that the most diverse genotypes were Maliyeshengchangguo and Changguozhongyueyin in dark jute, BZ-2-2, Aidianyehuangma, Yangjuchiyuanguo, Zijinhuangma and Jute 179 in white jute, which could be used as the potential parents in breeding programs for jute improvement. These results would be very useful for association studies and breeding in jute.

Development and Characterization of 1,906 EST-SSR Markers from Unigenes in Jute (Corchorus spp.).

Jute, comprising white and dark jute, is the second important natural fiber crop after cotton worldwide. However, the lack of expressed sequence tag-derived simple sequence repeat (EST-SSR) markers has resulted in a large gap in the improvement of jute. Previously, de novo 48,914 unigenes from white jute were assembled. In this study, 1,906 EST-SSRs were identified from these assembled uingenes. Among these markers, di-, tri- and tetra-nucleotide repeat types were the abundant types (12.0%, 56.9% and 21.6% respectively). The AG-rich or GA-rich nucleotide repeats were the predominant. Subsequently, a sample of 116 SSRs, located in genes encoding transcription factors and cellulose synthases, were selected to survey polymorphisms among12 diverse jute accessions. Of these, 83.6% successfully amplified at least one fragment and detected polymorphism among the 12diverse genotypes, indicating that the newly developed SSRs are of good quality. Furthermore, the genetic similarity coefficients of all the 12 accessions were evaluated using 97 polymorphic SSRs. The cluster analysis divided the jute accessions into two main groups with genetic similarity coefficient of 0.61. These EST-SSR markers not only enrich molecular markers of jute genome, but also facilitate genetic and genomic researches in jute.

Genetic Diversity of Kenaf (Hibiscus cannabinus) Evaluated by Inter-Simple Sequence Repeat (ISSR)

Understanding genetic diversity is very useful for scientific utilization for breeding. In this study, we estimated the genetic distances in a panel of 84 kenaf accessions collected from 26 countries and regions using ISSR markers. The results of UPGMA analysis showed that kenaf germplasm had abundant genetic variation, with genetic dissimilarity coefficients ranging from 0.01 to 0.62. The in-group dissimilarity coefficient (0.29) was observed in 84 kenaf accessions, and all the accessions could be divided into three groups: cultivars (L1–1), relatively wild species (L1–2 and L1–3), and wild species (the others). Further in-group analysis in group L1–1 (0.19) revealed that the kenaf cultivars could be divided into five subgroups with distinct regional characteristics. It is imperative that genes be exchanged among all kinds of tested varieties from different origins. The results provide a useful basis for kenaf germplasm research and breeding.

An Efficient Regeneration System and Optimization of the Transformation from the Cotyledonary Node of Jute (Corchorus capsularis L.)

The purpose of this study was to use cotyledonary nodes as explants to establish an efficient regeneration protocol for jute (Corchorus capsularis L.) on Murashige and Skoog (MS) basal medium. Research into the different growth regulators using the orthogonal design L16 (45) revealed that the best shoot induction medium is MS medium containing 8% (w/v) agar and 3% (w/v) sucrose supplemented with 1.0 mg/L 6BA and 0.25 mg/L NAA. The average number of shoots per explant and the explant induction rate were 9.8 and 100%. After 3 weeks, 2–3 cm shoots were rooting on 1/2 MS medium containing 8% (w/v) agar and 3% (w/v) sucrose supplemented with 1.0 mg/L 6-BA + 0.2 mg/L NAA. Moreover, we optimized Agrobacterium-mediated transformation using the GUS gene transient expression system. The best condition for obtaining higher transformation rate consisted of the use of fresh explants to which 100 μM acetosyringone was added for a co-culture time of 10 min, the OD value of Agrobacterium liquid is 0.5 at 600 nm. These data provide an important basis for the application of other trait gene in the improvement of jute fiber quality.