Transcriptome Analysis Reveals Genes Respond to Chlorophyll Deficiency in Green and Yellow Leaves of Chrysanthemum morifolium Ramat

Chlorophyll is vital for photosynthesis to produce sugars and other useful biochemical products in green plants. However, the molecular effects of chlorophyll deficiency in Chrysanthemum are largely unknown. In this study, we identified a bud sport mutant chrysanthemum belonging to the variety ‘Nannong Binyun’, which has yellow branches. Plant physiological studies have shown that the yellow color is revealed due to chlorophyll loss. RNA extracts of yellow and green tissues were analyzed using high-throughput RNA-sequencing, and a total of 11,649 tissue enriched unigenes that respond to chlorophyll deficiency were identified, including 4803 unigenes upregulated in yellow tissues and 6846 unigenes in green tissues. GO analysis revealed that these tissue-enriched genes may involve in the physiological processes of chlorophyll accumulation and photosynthesis. In addition, many DEGs from the families of AP2-EREBP, bHLH, MYB, and FAR1 that are associated with plant development and stress response were detected. Our study found that most of the genes from the GRAS family were downregulated in yellow leaves, indicating their putative roles in stem cell maintenance and possible contribution to leaf size determination.

Cytological and Transcriptomic Analysis Provide Insights into the Formation of Variegated Leaves in Ilex × altaclerensis ‘Belgica Aurea’

Ilex × altaclerensis ‘Belgica Aurea’ is an attractive ornamental plant bearing yellow-green variegated leaves. However, the mechanisms underlying the formation of leaf variegation in this species are still unclear. Here, the juvenile yellow leaves and mature variegated leaves of I. altaclerensis ‘Belgica Aurea’ were compared in terms of leaf structure, pigment content and transcriptomics. The results showed that no obvious differences in histology were noticed between yellow and variegated leaves, however, ruptured thylakoid membranes and altered ultrastructure of chloroplasts were found in yellow leaves (yellow) and yellow sectors of the variegated leaves (variegation). Moreover, the yellow leaves and the yellow sectors of variegated leaves had significantly lower chlorophyll compared to green sectors of the variegated leaves (green). In addition, transcriptomic sequencing identified 1675 differentially expressed genes (DEGs) among the three pairwise comparisons (yellow vs. green, variegation vs. green, yellow vs. variegation). Expression of magnesium-protoporphyrin IX monomethyl ester (MgPME) [oxidative] cyclase, monogalactosyldiacylglycerol (MGDG) synthase and digalactosyldiacylglycerol (DGDG) synthase were decreased in the yellow leaves. Altogether, chlorophyll deficiency might be the main factors driving the formation of leaf variegation in I.altaclerensis ‘Belgica Aurea’.

Genetic characterization and molecular mapping of novel chlorophyll deficiency gene in air-cured tobacco (Nicotiana tabacum L.)

This study was performed to genetical and morphological investigation of a novel chlorophyll deficiency gene in tobacco leaf. One low chlorophyll content (LCC) variety (Urumieh 2) and high chlorophyll content (HCC) variety (Burley Ree 103) from the Burley type was crossed and the F2 generation was grown on the field. One hundred plants were selected, contained low and high chlorophyll content. These plants were sampled and DNA was extracted. Sixty RAPD primers were tested on parents, LCC and HCC Bulks based on Bulk Segregant Analysis (BSA). Chi-square test confirmed the monogenic segregation. Regresion analysis showed that there was strong relationship between greenness degree and chlorophyll contents. Four primers (OPE17, OPC09, OPB08 and OPR02) showed polymorphism and after the test on 97 samples from the F2 generation two markers were selected (OPB08-1050 and OPC09-1900). That showed 15.9 and 10.8 CM distance from chlorophyll locus respectively.

Pollen Selection for Drought Tolerance in Sunflower

The drought resistance and genetic structure of F2 sporophytic populations for some morphological marker traits after pollen selection for water stress tolerance in F1 sunflower hybrids has been studied. The emasculated inflorescences were moistened with 10% and 20% of PEG 6000 solution in the experiments and with distilled water in the control. Freshly collected pollen was used for pollination after drying up the PEG solution on stigmas. F2 resulted seeds were germinated in 20% solution of PEG 6000 for a period of 3 days, and then the percentage of seed germination was counted. Germinated and not germinated seeds were separately planted. Segregation ratios in F2 populations for leaf venation and leaf chlorophyll deficiency marker traits were analyzed at early stage of development. Pollen treatment significantly increased the drought resistance of F2 populations and changed the monogenic ratios for leaf chlorophyll deficiency marker trait.