Identification, characterization, and expression profiles of the GASA genes in cotton

[Background] GASA (Giberellic Acid Stimulated in Arabidopsis) gene family plays a crucial role in the phytohormone signaling pathway, growth and development, and stress responses in plants. Many GASA homologs have been identified in various plants. Nevertheless, little is known about these proteins in cotton.

[Results] In the current study, we identified 19, 17, 25, 33, and 38 GASA genes via genome-wide analyses of Gossypium herbaceumG. arboreum, G. raimondiiG. barbadense, and G. hirsutum, respectively, and performed comprehensive bioinformatics and expression analyses. According to our results, 132 GASA proteins shared similar protein structures and were classified into four groups based on the phylogenetic tree. A synteny analysis suggested that segmental duplication was a key driver in the expansion of the GASA gene family. Meanwhile, the cis-element and protein interaction analyses indicated that GhGASA proteins play a significant role in the hormone responses. Transcriptomic and qRT-PCR (Quantitative real time-polymerase chain reaction) analyses revealed diverse expression profiles of the GhGASA genes in different organs under abiotic stresses, indicating that some GhGASA genes possibly participate in fiber development and abiotic-stress responses.

[Conclusion] The GASA genes in cotton were systematically identified and analyzed for the first time in this paper, and it suggested that the GASA genes are important to the development and growth of cotton. These results will support future exploration of the functions of GASA genes in cotton.

[Title] Identification, characterization, and expression profiles of the GASA genes in cotton

[Authors] QIAO Kaikai, MA Changkai, LV Jiaoyan, ZHANG Chaojun, MA Qifeng and FAN Shuli

Journal of Cotton Research 2021, 47

Insights into wing dimorphism in worldwide agricultural pest and host-alternating aphid Aphis gossypii

[Background] The worldwide pest Aphis gossypii has three-winged morphs in its life cycle, namely, winged parthenogenetic female (WPF), winged gynopara (GP), and winged male, which are all produced by a wingless parthenogenetic female (WLPF). Most studies on A. gossypii have focused on WPF, while few have investigated GP and male. The shared molecular mechanism underlying the wing differentiation in the three wing morphs of A. gossypii remains unknown. The wing differentiation of WPF was explored in a previous study. Herein, GP and male were induced indoors. The characters of the body, internal genitals, wing veins, and fecundity of GP and male were compared with those of WPF or WLPF. Compared with WLPF, the shared and separate differentially expressed genes (DEGs) were identified in these three-wing morphs.

[Results] Newly-born nymphs reared in short photoperiod condition (8 L:16D, 18 °C) exclusively produced gynoparae (GPe) and males in adulthood successively, in which the sex ratio was GP biased. A total of 14 GPe and 9 males were produced by one mother aphid. Compared with WLPF, the three-wing morphs exhibited similar morphology and wing vein patterns but were obviously discriminated in the length of fore- and underwings, reproductive system, and fecundity. A total of 37 090 annotated unigenes were obtained from libraries constructed using the four morphs via RNA sequencing (RNA-Seq). In addition, 10 867 and 19 334 DEGs were identified in the pairwise comparison of GP versus WLPF and male versus WLPF, respectively. Compared with WLPF, the winged morphs demonstrated 2 335 shared DEGs (1 658 upregulated and 677 downregulated). The 1 658 shared upregulated DEGs were enriched in multiple signaling pathways, including insulin, FoxO, MAPK, starch and sucrose metabolism, fatty acid biosynthesis, and degradation, suggesting their key roles in the regulation of wing plasticity in the cotton aphid. Forty-four genes that spanned the range of differential expression were chosen to validate statistical analysis based on RNA-Seq through the reverse transcription quantitative real time polymerase chain reaction (RT-qPCR). The comparison concurred with the expression pattern (either up- or downregulated) and supported the accuracy and reliability of RNA-Seq. Finally, the potential roles of DEGs related to the insulin signaling pathway in wing dimorphism were discussed in the cotton aphid.

[Conclusion] The present study established an efficiently standardized protocol for GP and male induction in cotton aphid by transferring newly-born nymphs to short photoperiod conditions (8 L:16D, 18 °C). The external morphological characters, especially wing vein patterns, were similar among WPFs, GPe, and males. However, their reproductive organs were strikingly different. Compared with WLPF, shared (2 335) and exclusively (1 470 in WLPF, 2 419 in GP, 10 774 male) expressed genes were identified in the three-wing morphs through RNA-Seq, and several signaling pathways that are potentially involved in their wing differentiation were obtained, including insulin signaling, starch and sucrose metabolism.

[Title] Insights into wing dimorphism in worldwide agricultural pest and host-alternating aphid Aphis gossypii

[Authors] JI Jichao, HUANGFU Ningbo, LUO Junyu, GAO Xueke, NIU Lin, ZHANG Shuai & CUI Jinjie

Journal of Cotton Research 2021, 45

Genome-wide identification and expression analysis of the GhIQD gene family in upland cotton (Gossypium hirsutum L.)

[Background] Calmodulin (CaM) is one of the most important Ca2+ signaling receptors because it regulates diverse physiological and biochemical reactions in plants. CaM functions by interacting with CaM-binding proteins (CaMBPs) to modulate Ca2+ signaling. IQ domain (IQD) proteins are plant-specific CaMBPs that bind to CaM by their specific CaM binding sites.

[Results] In this study, we identified 102 GhIQD genes in the Gossypium hirsutum L. genome. The GhIQD gene family was classified into four clusters (I, II, III, and IV), and we then mapped the GhIQD genes to the G. hirsutum L. chromosomes. Moreover, we found that 100 of the 102 GhIQD genes resulted from segmental duplication events, indicating that segmental duplication is the main force driving GhIQD gene expansion. Gene expression pattern analysis showed that a total of 89 GhIQD genes expressed in the elongation stage and second cell wall biosynthesis stage of the fiber cells, suggesting that GhIQD genes may contribute to fiber cell development in cotton. In addition, we found that 20 selected GhIQD genes were highly expressed in various tissues. Exogenous application of MeJA significantly enhanced the expression levels of GhIQD genes.

[Conclusion] Our study shows that GhIQD genes are involved in fiber cell development in cotton and are also widely induced by MeJA. Thw results provide bases to systematically characterize the evolution and biological functions of GhIQD genes, as well as clues to breed better cotton varieties in the future.

[Title]Genome-wide identification and expression analysis of the GhIQD gene family in upland cotton (Gossypium hirsutum L.)

[Authors] DOU Lingling, LV Limin, KANG Yangyang, TIAN Ruijie, HUANG Deqing, LI Jiayin, LI Siyi, LIU Fengping, CAO Lingyan, JIN Yuhua, LIU Yang, LI Huaizhu, WANG Wenbo, PANG Chaoyou, SHANG Haihong, ZOU Changsong, SONG Guoli & XIAO Guanghui

Journal of Cotton Research 2021, 44

QTL mapping of agronomic and economic traits for four F2 populations of upland cotton

[Background] Upland cotton (Gossypium hirsutum) accounts for more than 90% of the annual world cotton output because of its high yield potential. However, yield and fiber quality traits often show negative correlations. We constructed four F2 populations of upland cotton, using two normal lines (4133B and SGK9708) with high yield potential but moderate fiber quality and two introgression lines (Suyuan04–3 and J02–247) with superior fiber quality, and used them to investigate the genetic basis underlying complex traits such as yield and fiber quality in upland cotton. We also phenotyped eight agronomic and economic traits and mapped quantitative trait loci (QTLs).

[Results] Extensive phenotype variations and transgressive segregation were found across the segregation populations. We constructed four genetic maps of 585.97 centiMorgan (cM), 752.45 cM, 752.45 cM, and 1 163.66 cM, one for each of the four F2 populations. Fifty QTLs were identified across the four populations (7 for plant height, 27 for fiber quality and 16 for yield). The same QTLs were identified in different populations, including qBW4 and qBW2, which were linked to a common simple sequence repeat (SSR) marker, NAU1255. A QTL cluster containing eight QTLs for six different traits was characterized on linkage group 9 of the 4133B × Suyuan04–3 population.

[Conclusion] These findings will provide insights into the genetic basis of simultaneous improvement of yield and fiber quality in upland cotton breeding.

[Title] QTL mapping of agronomic and economic traits for four F2 populations of upland cotton

[Authors] LI Hongge, PAN Zhaoe, HE Shoupu, JIA Yinhua, GENG Xiaoli, CHEN Baojun, WANG Liru, PANG Baoyin & DU Xiongming

Journal of Cotton Research 2021, 43