Pollen morphological assessment of specific selected species of district Sheikhupura, Punjab, Pakistan under LM and SEM.

Around 30 pollen samples, 16 families and 25 genera that were gathered, identified and preserved from 6 different localities of District Sheikhupura. Light and scanning electron microscopy was done for all collected flora. Out of the total samples, 43% specie was identified as herbs, 23% as shrubs, and 33% were identified as trees. The flora was both wild and cultivated. Wild plants were 33%, cultivated 40% and 26% of them were both wild and cultivated. Qualitative and Quantitative survey of pollens revealed polar shape of pollens were 37% spheroidal, 20% prolate spheroidal, 17% oblate spheroidal, remaining were rectangular and pecolpate. Sexine and nexine were available in 100% of samples. Thirty-three percentage of pollen grains were having spines on them. The presence of spines on pollen grains represents the evolutionary relationship amongst the plants. Current study was conducted to record and analyze palynomorphic diversity in district Sheikhupura, Punjab, Pakistan.

The ATP-binding cassette (ABC) transporter OsABCG3 is essential for pollen development in rice.

BACKGROUND: The pollen wall, which protects male gametophyte against various stresses and facilitates pollination, is essential for successful reproduction in flowering plants. The pollen wall consists of gametophyte-derived intine and sporophyte-derived exine. From outside to inside of exine are tectum, bacula, nexine I and nexine II layers. How these structural layers are formed has been under extensive studies, but the molecular mechanisms remain obscure. RESULTS: Here we identified two osabcg3 allelic mutants and demonstrated that OsABCG3 was required for pollen development in rice. OsABCG3 encodes a half-size ABCG transporter localized on the plasma membrane. It was mainly expressed in anther when exine started to form. Loss-function of OsABCG3 caused abnormal degradation of the tapetum. The mutant pollen lacked the nexine II and intine layers, and shriveled without cytoplasm. The expression of some genes required for pollen wall formation was examined in osabcg3 mutants. The mutation did not alter the expression of the regulatory genes and lipid metabolism genes, but altered the expression of lipid transport genes. CONCLUSIONS: Base on the genetic and cytological analyses, OsABCG3 was proposed to transport the tapetum-produced materials essential for pollen wall formation. This study provided a new perspective to the genetic regulation of pollen wall development.

Arabidopsis AT-hook protein TEK positively regulates the expression of arabinogalactan proteins for Nexine formation.

Nexine is a conserved layer of the pollen wall. We previously reported that the nexine layer is absent in the knockout mutant of Arabidopsis TRANSPOSABLE ELEMENT SILENCING VIA AT-HOOK (TEK) gene. In this study, we investigated the molecular regulatory functions of TEK in pollen development and identified the genes encoding Arabinogalactan proteins (AGPs) as direct targets of TEK, which are essential for nexine formation. Phenotypic similarity between tek and the TEK-SRDX transgenic lines suggest that TEK plays a role in transcriptional activation in anther development. Microarray analysis identified a total of 661 genes downregulated in tek, including four genes encoding AGPs, AGP6, AGP11, AGP23, and AGP40. Electrophoretic mobility shift assays showed that TEK could directly bind the nuclear matrix attachment region (MAR) and the promoter of AGP6. Chromatin immunoprecipitation followed by PCR analysis demonstrated that TEK is enriched in the promoters of the four AGP genes. Expression of AGP6 driven by the TEK promoter in tek partially rescued both nexine formation and plant fertility. These results indicate that TEK directly regulates AGP expression in the anther to control nexine layer formation. We also proposed that glycoproteins might be essential components of the nexine layer in the pollen wall.