Tropical Plant Biology

Gioppato, Helena; Dornelas, Marcelo

2018 Tropical Plant Biology

doi: 10.1007/s12042-018-9212-4

Flowering plants (angiosperms) are the most species-rich and structurally diverse group of living plants. This evolutionary success is in great part due to morphological novelties characteristic to angiosperms such as the flower. The molecular mechanisms that allowed flowers to be formed and diversified are still unknown but certainly key roles are played by particular members of the MADS-box gene family. They encode transcriptional factors fundamental to several developmental processes, including the organization of floral structure in angiosperms. Studies concerning the evolution of the MADS-box gene family in flowering plants have uncovered several duplication events, followed by functional diversification of members of this gene family belonging to the so called ABC model. According to the literature, some of these duplication events involved B-class MADS-box genes and contributed to the diversification of angiosperm flower morphologies. In this review, we focus on examples of B-class gene duplications and their implications for flower structure and adaptation.

Cao, Minghao; Zheng, Jian; Zhao, Yihong; Zhang, Zhiqiang; Zheng, Zhi-Liang

2018 Tropical Plant Biology

doi: 10.1007/s12042-018-9213-3

Citrus represents the most important non-climacteric fruits and thus understanding transcriptional control during fruit development is important for improving fruit yield and quality. Compared to relatively intensive transcriptomic studies of ripening citrus fruits, much less is known regarding expanding fruits. To provide a systems view of hormone response and transcriptional regulation in citrus fruit development from Stage I (slow fruit growth) to Stage II (rapid growth), we re-analyzed the fruit transcriptomes which we previously collected from the sweet orange varieties, Newhall, Xinhui, Bingtang, and Succari (Citrus sinensis L. Osbeck). A total of 3145 genes were differentially expressed across all four varieties, indicating that they likely have conserved functions in orange fruit development. Using a gene coexpression network-based systems approach, we constructed the subnetworks respectively for gibberellin response, ethylene response, transcription factors and chromatin modifications. Analysis of these subnetworks has led to the identification of more than a dozen major hub genes, such as EXPA1, GASA1/14, ERF13, HB22, ATK1, and TOPII, which represent the most promising candidates for future functional characterization.

Premachandran, M.; Lekshmi, Maya; Viola, V.; Remadevi, A.; Pazhany, Adhini

2018 Tropical Plant Biology

doi: 10.1007/s12042-018-9214-2

Erianthus arundinaceus (Retz.) Jesweit is a tropical wild grass used in sugarcane (Saccharum L.) breeding for introgression of disease resistance and high cane yield traits. In the backcross (BC2) hybrids of Saccharum officinarum × E. arundinaceus and S. spontaneum × E. arundinaceus, with E. arundinaceus as pollen parent, the progeny had plants morphologically resembling E. arundinaceus. These plants were with chromosome number 2n = 60, same as that of E. arundinaceus. Through genomic in situ hybridization it was found that all the chromosomes were of E. arundinaceus. PCR-RFLP studies of the chloroplast and mitochondrial DNA polymorphism revealed that these plants had Erianthus type cytoplasmic genomes rather than the expected maternal Saccharum type. Target region amplification polymorphism of molecular markers, comparison of morphological characters and pollen size deviation studies confirmed the possible origin of E. arundinaceus type progeny. The diploid pollen from E. arundinaceus plants is considered to be resulted in the diploid androgenesis or paternal apomixis. The diploid androgenesis with paternal transmission of chloroplast and mitochondrial genomes along with the nuclear genome of E. arundinaceus in backcross progeny of Saccharum × Erianthus intergeneric hybrids is the first report in angiosperms.

Wu, Yi; Yang, Yaodong; Qadri, Rashad; Iqbal, Amjad; Li, Jing; Fan, Haikuo; Wu, Yaoting

2018 Tropical Plant Biology

doi: 10.1007/s12042-018-9215-1

Coconut is an important tropical fruit and oil crop. Its long generation time, low multiplication rate and recalcitrant seeds make coconut more difficult for breeding and selection. New technologies and extensive resources to evaluate coconut breeding strategies are the demand of today. Molecular markers had the potential to dramatically increase the efficiency and efficacy in the areas of germplasm management, genotype identification and marker-assisted selection of economically important traits of coconut. However, the lack of relevant molecular techniques impedes the development of a new strategy for the genetic improvement of the coconut. In this study, we have successfully developed 84 SSR markers by Selectively Amplified Microsatellite from coconut genome and more than 90% of these SSR showed good transferability to the palm family. The study will enrich the genomic-SSR pool for coconut and also for the other palm tree. Besides, it will provide the scientists with more options for coconut germplasm evaluation, constructing a coconut genetic linkage map and designing the breeding programs for producing superior cultivars of coconut.