The gland localized CGP1 controls gland pigmentation and gossypol accumulation in cotton

Abstract

Summary Pigment glands, also known as black glands or gossypol glands, are specific for Gossypium spp. These glands strictly confine large amounts of secondary metabolites to the lysigenous cavity, leading to the glands’ intense colour and providing defence against pests and pathogens. This study performed a comparative transcriptome analysis of glanded versus glandless cotton cultivars. Twenty‐two transcription factors showed expression patterns associated with pigment glands and were characterized. Phenotypic screening of the genes, via virus‐induced gene silencing, showed an apparent disappearance of pigmented glands after the silencing of a pair of homologous MYB‐encoding genes in the A and D genomes (designated as CGP1). Further study showed that CGP1a encodes an active transcription factor, which is specifically expressed in the gland structure, while CGP1d encodes a non‐functional protein due to a fragment deletion, which causes premature termination. RNAi‐mediated silencing and CRISPR knockout of CGP1 in glanded cotton cultivars generated a glandless‐like phenotype, similar to the dominant glandless mutant Gl2e. Microscopic analysis showed that CGP1 knockout did not affect gland structure or density, but affected gland pigmentation. The levels of gossypol and related terpenoids were significantly decreased in cgp1 mutants, and a number of gossypol biosynthetic genes were strongly down‐regulated. CGP1 is located in the nucleus where it interacts with GoPGF, a critical transcription factor for gland development and gossypol synthesis. Our data suggest that CGP1 and GoPGF form heterodimers to control the synthesis of gossypol and other secondary metabolites in cotton.

Identification of NHXs in Gossypium species and the positive role of GhNHX1 in salt tolerance

“…Plant NHX family plays an important role in salt resistance; however, research involving NHXs is still rare in cotton. The rapid development of biotechnology accelerated the molecular breeding process in cotton that allows us to study cotton NHXs in the genome-wide level [23][24][25][26][27]. Recently, GhSOS1, homologous to AtSOS1, was isolated from a salt-tolerant genotype of G. hirsutum.…”

Molecular cloning and characterization of GhERF105, a gene contributing to the regulation of gland formation in upland cotton (Gossypium hirsutum L.)

“…Therefore, 14 transcription factors were identified from the 289 DEGs (Supplementary Table S 3 ). The category of differentially expressed transcription factors genes encoded bHLH (GhMYC2-like) [ 32 ], followed by MYB (CGP1) [ 35 ], ERF (GhERF105), NAC and HSF. Programmed cell death (PCD) plays an important role during the development of pigment glands [ 42 ].…”

“…CGF3 (Cotton Gland Formation), identical to GoPGF gene, not only controls the gland morphogenesis directly, but also regulates gossypol biosynthesis indirectly [ 34 ]. CGP1 (Cotton Gland Pigmentation 1), which interacted with GoPGF , was identified by the comparative transcriptome analysis of glanded and glandless cotton accessions and involved in the regulation of gossypol biosynthesis but not gland formation [ 35 ]. In addition, the novel RanBP2 zinc finger protein (ZFP) and GauGRAS1 , which play the roles in the development of the cotton gland, were identified using suppression subtractive hybridization (SSH) from upland cotton ‘Xiangmian 18’ [ 9 , 36 – 38 ].…”

Molecular cloning and characterization of GhERF105, a gene participated in the regulation of gland formation from cotton (Gossypium hirsutum L.)

“…Silencing GoPGF results in the apparent absence of glands in all tissues of gland cotton and leads to an almost complete lack of gossypol [34][35]. CGP1 modulates gossypol accumulation but not gland morphogenesis, Knockout of CGP1 by CRISPR/Cas9 and VIGS produces a strong reduction in gossypol levels [36]. Silencing GauGRAS1 by VIGS leads to glandless stems and petiole and didn't change the form of glands in the leaves in G. australe.…”

“…CGF3 (Cotton Gland Formation), which is identical to GoPGF gene, not only controls the gland morphogenesis directly, but also regulates gossypol biosynthesis indirectly [35]. CGP1 (Cotton Gland Pigmentation 1), which interacted with GoPGF, was identi ed through comparative transcriptome analysis of glanded and glandless cotton accessions and was involved in the regulation of gossypol biosynthesis but not gland formation [36]. In addition, the novel RanBP2 zinc nger protein (ZFP) and GauGRAS1, which played the roles in the development of the cotton gland, were identi ed using suppression subtractive hybridization (SSH) from upland cotton 'Xiangmian 18' [9,[37][38][39].…”