LlSR28 is involved in pollen germination by affecting filamentous actin dynamics . Alternative splicing plays important roles in gene regulation and contributes to protein complexity . Previous studies suggest that alternative splicing exists in members of the villin / gelsolin / fragmin superfamily . In this study , a serine / argine - rich ( SR ) protein cDNA with 28 kDa protein ( LlSR28 ) was isolated from a lily ( Lilium longiflorum ) expression library . Protein domain analysis showed that LlSR28 had similar structures to Arabidopsis SR45 ( AtSR45 ) , and LlSR28 could complement the phenotype of loss of AtSR45 function . Therefore , overexpression of LlSR28 and AtSR45 mutant ( atsr45-1 ) were used in the following experiments . Overexpression of LlSR28 in Arabidopsis completely inhibited pollen germination . In contrast , the pollen germination of atsr45-1 was earlier than that of wild - type . In addition , pollen of atsr45-1 contained less F - actin at the corresponding hydration stage during pollen germination compared to that of wild - type . Alternative splicing analysis showed that Arabidopsis villin1 ( AtVLN1 ) transcript encoding the full - length protein was increased , and that encoding the truncated protein was decreased in atst45-1 . Moreover , the mRNA expression level of other actin - binding proteins ( ABPs ) abundant in Arabidopsis pollen was also changed in atsr45-1 . In conclusion , we hypothesize that LlSR28 alters F - actin dynamics probably through its alternative splicing activities to affect directly or indirectly the alternative splicing of AtVLN1 and the expression of different ABPs , which then affects the pollen germination .