**7. Tropical plants—a source of medicine**

Tropical plants are second major source of oxygen on the earth after oceanic phytoplankton. They are valuable indoor plants that can help to restore oxygen balance in the closed space and are an exclusive part of the top-five indoor plant species having the ability to produce maximum oxygen. These include Boston Fern (*Nephrolepis exaltata*), Peace Lily (*Spathiphyllum spp.*)*,* Snake Plant (*Sansevieria trifasciata),* and Areca Palm (*Dypsis lutescens*), and Gerber Daisy (*Gerbera jamesonii).* These tropical

plants play a critical role to moderate the level of carbon dioxide in the atmosphere. The modern world is highly reliant on fossil fuels to fulfill ever-increasing energy needs. This has led to an alarming increase in carbon accumulation in the atmosphere. Here comes the importance of carbon sinks for balancing carbon concentration. Grasslands, peat bogs, coastal ecosystems, coral reefs, wetlands, boreal forests, and tropical rainforests are important carbon sink ecosystems playing their role in balancing oxygen–carbon levels.

Tropical plants have also been explored as a source of valuable industrial products and drugs. Owing to the enriched biodiversity, they provide 60% of the chemical entities all over the world. They have been called the largest pharmacy in the world because more than 70% of the drugs are derived from these plants, directly or indirectly. Most synthetic drugs are also derivatives of tropical plant products. Half of the best 25 pharmaceutical agents also come from tropical forests. They have been identified as a valuable source of anticancer agents. Further, the first known antimalarial drug "quinine" was also derived from a neotropical tree [15].

#### **8. Technological interventions**

Indoor tropical plants not only act as oxygen balancing agents, but also have positive psychological effects, help in reducing indoor pollution, purifying indoor air, and absorbing volatile compounds such as formaldehyde, benzene, and trichloroethylene. Indoor air often contains volatile organic compounds such as formaldehyde, benzene, and chloroform. These toxins come from different sources including cooking, showering, furniture, and smoking. House plants can remove some toxins from the air, but they aren't very efficient: A homeowner would need more than 20 plants to remove formaldehyde from a typical room. Developing improved plants through recent innovative approaches can be of great help in this context (**Figure 2**). Researchers have worked out that the detoxification ability of the plants can be improved by the expression of the mammalian gene(s). Stuart strand and colleagues introduced a rabbit gene (*CYP2E1)* into a common houseplant, pothos ivy (*Epipremnum aureum*), and resultant plants were able to remove injected chloroform and benzene from the vial containing transgenic ivy plants [16].

Developing fancy indoor plants has gotten attention and different research groups have attempted to produce glowing plants. Mitiouchkina et al. [17] engineered tobacco plants with a fungal bioluminescence system that converts caffeic acid (present in the plants) into luciferin for the production of self-sustained luminescence, visible to the naked eye. Researchers have also engineered metabolic pathways to divert the natural supply of caffeic acid resulting in their ability to glow. Hence, these plants can glow throughout their life cycle. Likewise, transgenic papaya has been developed to stand against viral infection and is successfully grown in Hawaii. SunUp and Rainbow are the commonly grown varieties of virus-resistant transgenic papaya.

With the advent of next-generation techniques and advancements in DNA sequencing, it has become much more feasible to explore the genome of any plant for the desired traits. Evolutionary biology has got a great pace with these advancements. Phylogenetic and macroevolutionary analysis has been employed to define their genetic relatedness, thus helping out to track better plant species. Non-coding and repetitive DNA sequences play critical roles in determining the phenotype and genome evolution. The pan-genome analysis offers a valuable platform to evaluate the genetic diversity of species via investigation of their entire genome repertoire.

*Introductory Chapter: Integrative Technologies for Sustainable Plant Improvement DOI: http://dx.doi.org/10.5772/intechopen.107104*

**Figure 2.** *Integrative strategies and their applications to improve plants for better nutrition, medicine, and vaccines.*

It is now feasible to make multiple high-quality genomes that can be used to construct high-resolution pan-genomes making it possible to track all of the variations. However, high-throughput new tools would be required for the assembling, displaying, and interaction studies of such high-resolution pan-genomes.

Genome editing is one of the emerging innovations in the current millennium that has proved its potential to develop plants of desire. This innovative technology has been employed for stacking gene mutations, manipulating gene expression, and improvement of yield. Further, CRISPR-edited plants are not taken as conventional GMOs so, need not get approval from the regulatory bodies provided they are free from exogenous DNA. This has emerged as a user-friendly tool to address challenges in the production of tropical plants and improve their nutritional value. Numerous tropical plants have been targeted to improve through CRISPR/Cas9 and have achieved phenomenal successes during the last decade. Researchers at Cold Spring Harbor Laboratory precisely edited tomato genes involved in fruit size and shape, flowering time, self-pruning, and growth habitat, hence generating new alleles for valuable traits and improved plant architecture [18]. RAS-PDS1 and RAS-PDS2 (phytoene desaturase genes) were mutated in bananas to improve carotenoid biosynthesis, and it was reported to be improved by 59% [19]. Mutants of cassava plants were developed by targeting the MePDS gene and more than 95% of mutants exhibited partial albino or albino phenotype in cotyledonary-stage somatic embryos. Mutant embryos developed into plantlets indicating that 22–47% of the mutants were stable [20]. CRISPR-mediated editing of nCBP-1 and nCBP-2 (elF4E isoforms) in cassava resulted in improved resistance against cassava brown streak disease. Differential expression and genome-wide studies revealed numerous genes involved in salinity, drought, cold, and oxidative stresses. These genes can be targeted for improved tolerance against abiotic stresses in cassava. EgWRKY genes in African oil palm appeared to be upregulated in response to abiotic stresses. These findings revealed the crucial role of EgWRKY in abiotic stress tolerance, hence providing a great opportunity to edit the palm genome for enhanced abiotic stress tolerance. Likewise, S-genes mutations in papaya boosted its defense response against insect pests and pathogens by

increasing the accumulation of papain (a cysteine protease). Targeted mutation of TcNPR3NPR3 resulted in upregulation of PR gene expression and increased resistance against pathogens in Theobroma cacao. Though different tropical plants have been mutated through CRISPR/Cas9 system, certain limitations are there, which need to be addressed for the widespread applications of technology.
