The promoter sequence of sperm-expressed gene, PzIPT isolated from the S(vn) (sperm associated with the vegetative nucleus) of Plumbago zeylanica, was fused to a green fluorescent protein (GFP) reporter sequence and transformed into Arabidopsis thaliana to better visualize the live behavior of angiosperm sperm cells. Angiosperm sperm cells are not independently motile, migrating in a unique cell-within-a-cell configuration within the pollen tube. Sperm cells occur in association with the vegetative nucleus forming a male germ unit (MGU). In Arabidopsis, GFP was expressed equally in both sperm cells and was observed using a spinning disk confocal microscope, which allowed long duration observation of cells without bleaching or visible laser radiation damage. Pollen activation is reflected by conspicuous movement of sperm and pollen cytoplasm. Upon pollen germination, sperm cells enter the forming tube and become oriented, typically with a sperm cytoplasmic projection leading the sperm cells in the MGU, which remains intact throughout normal pollen tube elongation. Maturational changes, including vacuolization, general rounding and entry into G2, were observed during in vitro culture. When MGUs were experimentally disrupted by mild temperature elevation, sperm cells no longer tracked the growth of the tube and separated from the MGU, providing critical direct evidence that the MGU is a functional unit required for sperm transmission.

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Relationship between protein content (PC) in grains and grain yield in rice has not been clearly understood. Nipponbare and its five transgenic strains with different PCs in grains were used in the study to investigate their yield formation characteristics under the condition of field cultivation. There were two main results: (1) Under the same nitrogen amount, grain yields were lower in strains with higher PC in grains. Filled grain rate was very significantly and negatively correlated with PC in grains. With an increase in N fertilizer, PC in grains and grain yield significantly increased and the increase in yield was mainly dependent on the increase in panicle number and grains per panicle. (2) Under the same nitrogen amount, the strains with higher PC had less dry matter accumulation before heading stage, shorter functional period and lower photosynthetic rate of flag leaves after heading stage and lower apparent translocation amounts of dry matter and non-structure carbohydrates (NSC) from stems to grains during grain filling stage, leading to lower filled grain rate, which is the possible physiological reason for lower yield in those strains.