Extrafloral nectary–the sleeping beauty of plant science

Journal of Cotton Research

Abstract: Cotton is one of the most important cash crops, its growth season coincides with a high incidence of diverse groups of pests, leading to heavy use of pesticides. Recent identification of a signaling protein as a candidate regulator of cotton extrafloral nectary provides a new insight into the formation of sophisticated defense mechanisms in plants.

[Title] Extrafloral nectary–the sleeping beauty of plant science

[Author] CHEN Xiaoya

https://doi.org/10.1186/s42397-020-00051-7

QTL mapping for plant height and fruit branch number based on RIL population of upland cotton

Journal of Cotton Research

[Background] Plant height (PH) and fruit branch number (FBN) are important traits for improving yield and mechanical harvesting of cotton. In order to identify genes of PH and FBN in cotton germplasms to develop superior cultivars, quantitative trait loci (QTLs) for these traits were detected based on the phenotypic evaluation data in nine environments across four locations and 4 years and a previously reported genetic linkage map of an recombinant inbred line (RIL) population of upland cotton.

[Results] In total, 53 QTLs of PH and FBN, were identified on 21 chromosomes of the cotton genome except chromosomes c02, c09-c11, and c22. For PH, 27 QTLs explaining 3.81%–8.54% proportions of phenotypic variance were identified on 18 chromosomes except c02, c08-c12, c15, and c22. For FBN, 26 QTLs explaining 3.23%–11.00% proportions of phenotypic variance were identified on 16 chromosomes except c02-c03, c06, c09-c11, c17, c22-c23, and c25. Eight QTLs were simultaneously identified in at least two environments. Three QTL clusters containing seven QTLs were identified on three chromosomes (c01, c18 and c21). Eleven QTLs were the same as previously reported ones, while the rest were newly identified.

[Conclusions] The QTLs and QTL clusters identified in the current study will be helpful to further understand the genetic mechanism of PH and FBN development of cotton and will enhance the development of excellent cultivars for mechanical managements in cotton production.

[Title] QTL mapping for plant height and fruit branch number based on RIL population of upland cotton

[Authors] LIU Ruixian, XIAO Xianghui, GONG Juwu, LI Junwen, ZHANG Zhen, LIU Aiying, LU Quanwei, SHANG Haihong, SHI Yuzhen, GE Qun, IQBAL Muhammad Sajid, CHEN Quanjia, YUAN Youlu & GONG Wankui

https://doi.org/10.1186/s42397-020-0046-x

https://rdcu.be/b2bT3

The GhREV transcription factor regulate the development of shoot apical meristem in cotton (Gossypium hirsutum)

Journal of Cotton Research

[Background] Manual topping is a routine agronomic practice for balancing the vegetative and reproductive growth of cotton (Gossypium hirsutum) in China, but its cost-effectiveness has decreased over time. Therefore, there is an urgent need to replace manual topping with new approaches, such as biological topping. In this study, we examined the function of GhREV transcription factors (a class III homeodomain-leucine zipper family, HD-ZIP III) in regulating the development of shoot apical meristem (SAM) in cotton with the purpose of providing candidate genes for biological topping of cotton in the future.

[Results] We cloned four orthologous genes of AtREV in cotton, namely GhREV1GhREV2GhREV3, and GhREV4. All the GhREVs expressed in roots, stem, leaves, and SAM. Compared with GhREV1 and GhREV3, the expression level of GhREV2 and GhREV4 was higher in the SAM. However, only GhREV2 had transcriptional activity. GhREV2 is localized in the nucleus; and silencing it via virus-induced gene silencing (VIGS) produced an abnormal SAM. Two key genes, GhWUSA10 and GhSTM, which involved in regulating the development of plant SAM, showed about 50% reduction in their transcripts in VIGS-GhREV2 plants.

[Conclusion] GhREV2 positively regulates the development of cotton SAM by regulating GhWUSA10 and GhSTM potentially.

[Title] The GhREV transcription factor regulate the development of shoot apical meristem in cotton (Gossypium hirsutum)

[Authors] YANG Doudou, AN Jing, LI Fangjun, ENEJI A. Agrinya, TIAN Xiaoli & LI Zhaohu

https://doi.org/10.1186/s42397-020-0045-y

https://rdcu.be/b18jh

Identification of QTLs and candidate genes for physiological traits associated with drought tolerance in cotton

Journal of Cotton Research

[Background] Cotton is mainly grown for its natural fiber and edible oil. The fiber obtained from cotton is the indispensable raw material for the textile industries. The ever changing climatic condition, threatens cotton production due to a lack of sufficient water for its cultivation. Effects of drought stress are estimated to affect more than 50% of the cotton growing regions. To elucidate the drought tolerance phenomenon in cotton, a backcross population was developed from G. tomentosum, a drought tolerant donor parent and G. hirsutum which is highly susceptible to drought stress.

[Results] A genetic map of 10 888 SNP markers was developed from 200 BC2F2 populations. The map spanned 4 191.3 centi-Morgan (cM), with an average distance of 0.104 7 cM, covering 51% and 49% of At and Dt sub genomes, respectively. Thirty stable Quantitative trait loci (QTLs) were detected, in which more than a half were detected in the At subgenome. Eighty-nine candidate genes were mined within the QTL regions for three traits: cell membrane stability (CMS), saturated leaf weight (SLW) and chlorophyll content. The genes had varied physiochemical properties. A majority of the genes were interrupted by introns, and only 15 genes were intronless, accounting for 17% of the mined genes. The genes were found to be involved molecular function (MF), cellular component (CC) and biological process (BP), which are the main gene ontological (GO) functions. A number of miRNAs were detected, such as miR164, which is associated with NAC and MYB genes, with a profound role in enhancing drought tolerance in plants. Through RT-qPCR analysis, 5 genes were found to be the key genes involved in enhancing drought tolerance in cotton. Wild cotton harbors a number of favorable alleles, which can be exploited to aid in improving the narrow genetic base of the elite cotton cultivars. The detection of 30 stable QTLs and 89 candidate genes found to be contributed by the donor parent, G. tomentosum, showed the significant genes harbored by the wild progenitors which can be exploited in developing more robust cotton genotypes with diverse tolerance levels to various environmental stresses.

[Conclusion] This was the first study involving genome wide association mapping for drought tolerance traits in semi wild cotton genotypes. It offers an opportunity for future exploration of these genes in developing highly tolerant cotton cultivars to boost cotton production.

[Title] Identification of QTLs and candidate genes for physiological traits associated with drought tolerance in cotton

[Authors] MAGWANGA Richard Odongo, LU Pu, KIRUNGU Joy Nyangasi, CAI Xiaoyan, ZHOU Zhongli, AGONG Stephen Gaya, WANG Kunbo & LIU Fang

https://doi.org/10.1186/s42397-020-0043-0

https://rdcu.be/b1502

Transient expression of SbDhr2 and MeHNL in Gossypium hirsutum for herbivore deterrence assay with Spodoptera litura

Journal of Cotton Research

[Background] Spodoptera litura (Lepidoptera: Noctuidae), commonly known as tobacco cutworm or cotton leafworm, is a polyphagous pest which causes considerable damage to cotton (Gossypium hirsutum) and other crops. Herbivore-induced defence response is activated in plants against chewing pests, in which plant secondary metabolites play an important role. Dhurrinase2 (SbDhr2), a cyanogenic β-glucosidase from Sorghum bicolor, is the key enzyme responsible for the hydrolysis of dhurrin (cyanogenic β-glucosidic substrate) to p-hydroxymandelonitrile. Hydroxynitrile lyase (MeHNL) from Mannihot esculanta catalyses the dissociation of cyanohydrins to hydrogen cyanide and corresponding carbonyl compound, both enzymes play a pivotal role in plant defence mechanism.

[Results] SbDhr2 and MeHNL genes were expressed individually and co-expressed transiently in cotton leaves. We examined the feeding response of S. litura to leaves in the choice assay. The Slitura population used in this study showed better feeding deterrence to leaves co-expressing both genes compared with the expression of an individual gene.

[Conclusion] Our results suggest that co-expression of SbDhr2 and MeHNL genes in cotton leaves demonstrate feeding deterrence to S. litura. Engineering cyanogenic pathway in aerial parts of cotton would be an additional defence strategy against generalist pests and can be enhanced against specialist pests.

[Title] Transient expression of SbDhr2 and MeHNL in Gossypium hirsutum for herbivore deterrence assay with Spodoptera litura

[Authors] MAHAJAN Chavi, NASER Rafiuddin & GUPTA Shantikumar

https://doi.org/10.1186/s42397-020-0044-z

https://jcottonres.biomedcentral.com/articles/10.1186/s42397-020-0044-z

Transgenic crops for the agricultural improvement in Pakistan

Transgenic technologies have emerged as a powerful tool for crop improvement in terms of yield, quality, and quantity in many countries of the world. However, concerns also exist about the possible risks involved in transgenic crop cultivation. In this review, literature is analyzed to gauge the real intensity of the issues caused by environmental stresses in Pakistan. In addition, the research work on genetically modified organisms (GMOs) development and their performance is analyzed to serve as a guide for the scientists to help them select useful genes for crop transformation in Pakistan. The funding of GMOs research in Pakistan shows that it does not follow the global trend. We also present socio-economic impact of GM crops and political dimensions in the seed sector and the policies of the government. We envisage that this review provides guidelines for public and private sectors as well as the policy makers in Pakistan and in other countries that face similar environmental threats posed by the changing climate.

GENE FLOW FROM MAJOR GENETICALLY MODIFIE D CROPS AND STRATEGIES FOR C ONTAINMENT AND MITIG ATION OF TRANSGENE ESCAPE: A

Recent advancements in biotechnology resulted in rapid adoption of genetically modified (GM) crops in the agriculture systems. At the same time, transgene escape has also been reported and examples reveal global dimension of the problem. Pollen mediated gene flow (PMGF) is the major pathway for transgene escape. Almost all transgenes have been escaped into their Non-GM counterpart and wild relatives. Although gene flow varies between species, crops, and ecological zones/environments but intraspecific gene flow (> 10%) is not uncommon in adjacent populations. Whereas in outcrossing species, 1% gene flow at thousand meters’ isolation is not unusual, and magnitude is even higher than the mutation rate. It is well documented that transgene flow is deteriorating different production systems in agriculture and famers choice to cultivate GM, conventional and organic crops. If comprehensive policy is not implemented, then in future it will be difficult to detect and remove transgenes from the environment; if unexpected problems arise.

Genetic effects conferring heat tolerance in upland cotton (Gossypium hirsutum L.)

Cotton belongs to family Malvaceae containing more than
200 genera and about 2 300 species. There are more than
50 species of Gossypium reported till now, which are native
to Africa, Australia, Central and South America and Asia,
respectively (Fryxell 1992; Wendel and Grover 2015). Out
of 50 species, only four are domesticated and widespread.
Two diploid (2n = 26) species, namely G. arboreum and G.
herbaceum belong to Old World cotton produce only 1%
of the total cotton production in the world, whereas two
tetraploid (2n = 52) species, namely G. barbadense and G.
hirsutum belong to New World cotton produce 94% of the
total world cotton production. G. barbadense produces 4%,
while G. hirsutum also known as upland cotton produces
about 90% of the total cotton production in the world (Lu
et al. 1997; McCarty et al. 2004).
Upland cotton is a key source of spinnable fiber and cultivated
in more than 61 countries in the world on an area of
29.3 million hectares (ICAC 2018). Cotton and cottonbased
industry has a pivoting role in the economy of
Pakistan. Pakistan ranks the fourth in terms of area and
production in the world after India, China and USA, 3rd in
consumption and 2nd in yarn production in the world.
Cotton contributes 1% share in GDP, while 55% in total foreign
exchange earnings of Pakistan. Cotton was planted on
an area of 2.7 million hectares in 2017, showing an increase
of 10% over the previous year. About 8% more cotton production,
i.e., 11.54 million bales was recorded during 2017/
2018 as compared with 2016/2017 where 10.72 million
bales was recorded (PCCC 2017). However, in terms of per
acre yield (679 kg·hm− 2), Pakistan is lagging far behind
from the major cotton producing countries like Australia
(1 816 kg·hm− 2), China (1 719 kg·hm− 2), Turkey (1 826
kg·hm− 2) and USA (985kg·hm− 2) (ICAC 2018).
A loss of about one-third of cotton produce was recorded
in Pakistan during 2015/2016 due to adverse climatic conditions
particularly heavy rains during reproductive phase
of crop. But high temperature with dry weather conditions
favored the spread of whitefly in 2016 and 2017 which affected
the productivity of cotton crop on a wide range of
area in Punjab province. In recent times besides drought,
salinity, insect pests, diseases and seed quality: high
temperature has emerged as a major threat to cotton productivity.
It is estimated that the global temperature is increasing
by 0.4~0.8 °C/year (PMD 2016). The consequences
of high temperature in cotton could be low germination,
higher fruit shedding (≥ 30 °C/22 °C), pollen sterility and
abortion (Guilioni et al. 1997; Ismail and Hall 1999), unavailability
of macro and micro nutrients due to increase in
soil pH, higher levels of CO2 in the air will increase photosynthetic
activity resulting in enhanced nutrient requirement
of cotton plants.

Role of SNPs in determining QTLs for major traits in cotton

A single nucleotide polymorphism is the simplest form of genetic variation among individuals and can induce
minor changes in phenotypic, physiological and biochemical characteristics. This polymorphism induces various
mutations that alter the sequence of a gene which can lead to observed changes in amino acids. Several assays
have been developed for identification and validation of these markers. Each method has its own advantages and
disadvantages but genotyping by sequencing is the most common and most widely used assay. These markers are
also associated with several desirable traits like yield, fibre quality, boll size and genes respond to biotic and abiotic
stresses in cotton. Changes in yield related traits are of interest to plant breeders. Numerous quantitative trait loci
with novel functions have been identified in cotton by using these markers. This information can be used for crop
improvement through molecular breeding approaches. In this review, we discuss the identification of these markers
and their effects on gene function of economically important traits in cotton

Down regulation of cotton GbTRP1 leads to accumulation of anthranilates and confers resistance to Verticillium dahliae

Journal of Cotton Research

[Background] Verticillium wilt, caused by Verticillium dahliae, is called a “cancer” disease of cotton. The discovery and identification of defense-related genes is essential for the breeding of Verticillium wilt-resistant varieties. In previous research we identified some possible broad-spectrum resistance genes. Here, we report a tryptophan synthesis-related gene GbTRP1 and its functional analysis in relation to the resistance of cotton to V. dahliae.

[Results] Expression analysis shows that GbTRP1 is suppressed at 1 h and 6 h post V. dahliae infection, but activated at 12 h and 24 h, and the expression of GbTRP1 is highly induced by treatment with salicylic acid and jasmonic acid. Sub-cellular localization studies show that GbTRP1 is localized in the chloroplast. Suppression of GbTRP1 expression leads to lesion-mimic phenotypes and activates the immune response in cotton by showing enhanced resistance to V. dahliae and B. cinerea. Metabolomic analysis shows that anthranilic compounds significantly accumulated in GbTRP1-silenced plants, and these metabolites can inhibit the growth of V. dahliae and B. cinerea in vitro.

[Conclusions] Our results show that suppression of GbTRP1 expression dramatically activates the immune response and increases resistance of cotton to V. dahliae and B. cinerea, possibly due to the accumulation of anthranilate compounds. This study not only provides genetic resources for disease resistance breeding, but also may provide a basis for new chemical control methods for combatting of fungal disease in cotton.

[Title] Down regulation of cotton GbTRP1 leads to accumulation of anthranilates and confers resistance to Verticillium dahliae

[Authors] MIAO Yuhuan, ZHU Longfu and ZHANG Xianlong

Journal of Cotton Research. 2019; 2:19

https://doi.org/10.1186/s42397-019-0034-1

https://jcottonres.biomedcentral.com/articles/10.1186/s42397-019-0034-1